diff --git a/client/pool-buffer.c b/client/pool-buffer.c
index 3546b897..c47c40eb 100644
--- a/client/pool-buffer.c
+++ b/client/pool-buffer.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809
 #include <assert.h>
 #include <cairo.h>
 #include <errno.h>
diff --git a/common/gesture.c b/common/gesture.c
index 58170443..272aa837 100644
--- a/common/gesture.c
+++ b/common/gesture.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "gesture.h"
 
 #include <math.h>
diff --git a/common/ipc-client.c b/common/ipc-client.c
index d30212d2..a0be2b2d 100644
--- a/common/ipc-client.c
+++ b/common/ipc-client.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
diff --git a/common/log.c b/common/log.c
index 483420e7..3eacdb34 100644
--- a/common/log.c
+++ b/common/log.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200112L
 #include <signal.h>
 #include <stdarg.h>
 #include <stdio.h>
diff --git a/common/loop.c b/common/loop.c
index 80fe18ea..b99c6d55 100644
--- a/common/loop.c
+++ b/common/loop.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200112L
 #include <limits.h>
 #include <string.h>
 #include <stdbool.h>
diff --git a/common/stringop.c b/common/stringop.c
index c503143a..16d04917 100644
--- a/common/stringop.c
+++ b/common/stringop.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <stdarg.h>
 #include <stdbool.h>
diff --git a/common/util.c b/common/util.c
index 5d4c0673..7c492bcb 100644
--- a/common/util.c
+++ b/common/util.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <fcntl.h>
 #include <math.h>
diff --git a/meson.build b/meson.build
index f8bf4f80..1043e4ba 100644
--- a/meson.build
+++ b/meson.build
@@ -14,6 +14,7 @@ project(
 add_project_arguments(
 	[
 		'-DWLR_USE_UNSTABLE',
+		'-D_POSIX_C_SOURCE=200809L',
 
 		'-Wno-unused-parameter',
 		'-Wno-unused-result',
diff --git a/sway/commands.c b/sway/commands.c
index 6becf3c8..8d003dfa 100644
--- a/sway/commands.c
+++ b/sway/commands.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809
 #include <ctype.h>
 #include <stdarg.h>
 #include <stdlib.h>
diff --git a/sway/commands/assign.c b/sway/commands/assign.c
index f7d911f7..bf95cf00 100644
--- a/sway/commands/assign.c
+++ b/sway/commands/assign.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdio.h>
 #include <string.h>
 #include "sway/commands.h"
diff --git a/sway/commands/bar.c b/sway/commands/bar.c
index 22756acb..635e895b 100644
--- a/sway/commands/bar.c
+++ b/sway/commands/bar.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809
 #include <stdio.h>
 #include <string.h>
 #include <strings.h>
diff --git a/sway/commands/bar/font.c b/sway/commands/bar/font.c
index 891c87af..0c074679 100644
--- a/sway/commands/bar/font.c
+++ b/sway/commands/bar/font.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/bar/hidden_state.c b/sway/commands/bar/hidden_state.c
index 8b661e3a..7b38831e 100644
--- a/sway/commands/bar/hidden_state.c
+++ b/sway/commands/bar/hidden_state.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include <strings.h>
 #include "sway/commands.h"
diff --git a/sway/commands/bar/icon_theme.c b/sway/commands/bar/icon_theme.c
index 6ac07843..fee21709 100644
--- a/sway/commands/bar/icon_theme.c
+++ b/sway/commands/bar/icon_theme.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "config.h"
 #include "sway/commands.h"
diff --git a/sway/commands/bar/id.c b/sway/commands/bar/id.c
index a9a61743..46cf4ca9 100644
--- a/sway/commands/bar/id.c
+++ b/sway/commands/bar/id.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/bar/mode.c b/sway/commands/bar/mode.c
index 7c2f423b..d69e910b 100644
--- a/sway/commands/bar/mode.c
+++ b/sway/commands/bar/mode.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include <strings.h>
 #include "sway/commands.h"
diff --git a/sway/commands/bar/output.c b/sway/commands/bar/output.c
index cac1d056..51730176 100644
--- a/sway/commands/bar/output.c
+++ b/sway/commands/bar/output.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <string.h>
 #include "sway/commands.h"
diff --git a/sway/commands/bar/position.c b/sway/commands/bar/position.c
index b207de0b..94f530ec 100644
--- a/sway/commands/bar/position.c
+++ b/sway/commands/bar/position.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include <strings.h>
 #include "sway/commands.h"
diff --git a/sway/commands/bar/separator_symbol.c b/sway/commands/bar/separator_symbol.c
index 6737d4d2..50e9a873 100644
--- a/sway/commands/bar/separator_symbol.c
+++ b/sway/commands/bar/separator_symbol.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/bar/tray_output.c b/sway/commands/bar/tray_output.c
index eb3b486e..679facf7 100644
--- a/sway/commands/bar/tray_output.c
+++ b/sway/commands/bar/tray_output.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "config.h"
 #include "sway/commands.h"
diff --git a/sway/commands/bind.c b/sway/commands/bind.c
index 979e178f..268f2855 100644
--- a/sway/commands/bind.c
+++ b/sway/commands/bind.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <libevdev/libevdev.h>
 #include <linux/input-event-codes.h>
 #include <string.h>
diff --git a/sway/commands/exec_always.c b/sway/commands/exec_always.c
index 8fca1909..8bc1048c 100644
--- a/sway/commands/exec_always.c
+++ b/sway/commands/exec_always.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
diff --git a/sway/commands/font.c b/sway/commands/font.c
index 74bb6b9f..9920d03e 100644
--- a/sway/commands/font.c
+++ b/sway/commands/font.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/gesture.c b/sway/commands/gesture.c
index d4442cc3..90a20716 100644
--- a/sway/commands/gesture.c
+++ b/sway/commands/gesture.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 
 #include "gesture.h"
diff --git a/sway/commands/input/calibration_matrix.c b/sway/commands/input/calibration_matrix.c
index 38749fbb..53fe2c35 100644
--- a/sway/commands/input/calibration_matrix.c
+++ b/sway/commands/input/calibration_matrix.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include <strings.h>
 #include "sway/config.h"
diff --git a/sway/commands/input/map_from_region.c b/sway/commands/input/map_from_region.c
index 4400e111..2f8f753d 100644
--- a/sway/commands/input/map_from_region.c
+++ b/sway/commands/input/map_from_region.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <string.h>
 #include <strings.h>
diff --git a/sway/commands/input/map_to_output.c b/sway/commands/input/map_to_output.c
index f60fb7d5..a7266baa 100644
--- a/sway/commands/input/map_to_output.c
+++ b/sway/commands/input/map_to_output.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include <strings.h>
 #include "sway/config.h"
diff --git a/sway/commands/input/map_to_region.c b/sway/commands/input/map_to_region.c
index ad535db2..9087c589 100644
--- a/sway/commands/input/map_to_region.c
+++ b/sway/commands/input/map_to_region.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <string.h>
 #include "sway/commands.h"
diff --git a/sway/commands/input/xkb_file.c b/sway/commands/input/xkb_file.c
index 493f94fb..056f00e5 100644
--- a/sway/commands/input/xkb_file.c
+++ b/sway/commands/input/xkb_file.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <unistd.h>
 #include <errno.h>
 #include "sway/config.h"
diff --git a/sway/commands/input/xkb_layout.c b/sway/commands/input/xkb_layout.c
index 22626517..1d01886c 100644
--- a/sway/commands/input/xkb_layout.c
+++ b/sway/commands/input/xkb_layout.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/input/xkb_model.c b/sway/commands/input/xkb_model.c
index f4a33de3..a9144a8a 100644
--- a/sway/commands/input/xkb_model.c
+++ b/sway/commands/input/xkb_model.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/input/xkb_numlock.c b/sway/commands/input/xkb_numlock.c
index 87d3e60c..bbe848fe 100644
--- a/sway/commands/input/xkb_numlock.c
+++ b/sway/commands/input/xkb_numlock.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 #include "sway/commands.h"
 #include "util.h"
diff --git a/sway/commands/input/xkb_options.c b/sway/commands/input/xkb_options.c
index d609293f..7ca20777 100644
--- a/sway/commands/input/xkb_options.c
+++ b/sway/commands/input/xkb_options.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/input/xkb_rules.c b/sway/commands/input/xkb_rules.c
index 3b59622c..8fbd26fb 100644
--- a/sway/commands/input/xkb_rules.c
+++ b/sway/commands/input/xkb_rules.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/input/xkb_switch_layout.c b/sway/commands/input/xkb_switch_layout.c
index 3cce4ec8..ecac8e6c 100644
--- a/sway/commands/input/xkb_switch_layout.c
+++ b/sway/commands/input/xkb_switch_layout.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <wlr/interfaces/wlr_keyboard.h>
 #include "sway/config.h"
diff --git a/sway/commands/input/xkb_variant.c b/sway/commands/input/xkb_variant.c
index d0e21d77..2d14ea9c 100644
--- a/sway/commands/input/xkb_variant.c
+++ b/sway/commands/input/xkb_variant.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/config.h"
 #include "sway/commands.h"
 #include "log.h"
diff --git a/sway/commands/mark.c b/sway/commands/mark.c
index 30cf458c..2bfc86b3 100644
--- a/sway/commands/mark.c
+++ b/sway/commands/mark.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/mode.c b/sway/commands/mode.c
index 7263efcb..b3216967 100644
--- a/sway/commands/mode.c
+++ b/sway/commands/mode.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <string.h>
 #include "sway/commands.h"
diff --git a/sway/commands/move.c b/sway/commands/move.c
index 69ed06c0..bcbdaa2d 100644
--- a/sway/commands/move.c
+++ b/sway/commands/move.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <math.h>
 #include <stdbool.h>
diff --git a/sway/commands/output/background.c b/sway/commands/output/background.c
index d691295f..55bd7671 100644
--- a/sway/commands/output/background.c
+++ b/sway/commands/output/background.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <libgen.h>
 #include <stdio.h>
 #include <string.h>
diff --git a/sway/commands/reload.c b/sway/commands/reload.c
index 82967ca7..6c0aac26 100644
--- a/sway/commands/reload.c
+++ b/sway/commands/reload.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/seat/attach.c b/sway/commands/seat/attach.c
index 00bfdab6..47d18546 100644
--- a/sway/commands/seat/attach.c
+++ b/sway/commands/seat/attach.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/seat/cursor.c b/sway/commands/seat/cursor.c
index 5a8a3bc8..85c5edca 100644
--- a/sway/commands/seat/cursor.c
+++ b/sway/commands/seat/cursor.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <linux/input-event-codes.h>
 
 #include <strings.h>
diff --git a/sway/commands/seat/hide_cursor.c b/sway/commands/seat/hide_cursor.c
index e09b82d9..f5177a47 100644
--- a/sway/commands/seat/hide_cursor.c
+++ b/sway/commands/seat/hide_cursor.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/seat/idle.c b/sway/commands/seat/idle.c
index 62b94db2..2974453e 100644
--- a/sway/commands/seat/idle.c
+++ b/sway/commands/seat/idle.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <limits.h>
 #include <string.h>
 #include <strings.h>
diff --git a/sway/commands/seat/xcursor_theme.c b/sway/commands/seat/xcursor_theme.c
index 202f35b9..61322a57 100644
--- a/sway/commands/seat/xcursor_theme.c
+++ b/sway/commands/seat/xcursor_theme.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/set.c b/sway/commands/set.c
index c539e9fc..ba384c7c 100644
--- a/sway/commands/set.c
+++ b/sway/commands/set.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdio.h>
 #include <string.h>
 #include <strings.h>
diff --git a/sway/commands/show_marks.c b/sway/commands/show_marks.c
index fecb5ade..60cef9fa 100644
--- a/sway/commands/show_marks.c
+++ b/sway/commands/show_marks.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/swap.c b/sway/commands/swap.c
index d44eb006..e142eede 100644
--- a/sway/commands/swap.c
+++ b/sway/commands/swap.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <strings.h>
 #include "config.h"
 #include "log.h"
diff --git a/sway/commands/title_format.c b/sway/commands/title_format.c
index a2446b7e..0b2ea265 100644
--- a/sway/commands/title_format.c
+++ b/sway/commands/title_format.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/unmark.c b/sway/commands/unmark.c
index c3a6ac4b..4aba5bae 100644
--- a/sway/commands/unmark.c
+++ b/sway/commands/unmark.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <string.h>
 #include "sway/commands.h"
 #include "sway/config.h"
diff --git a/sway/commands/workspace.c b/sway/commands/workspace.c
index 03e488ba..a14ebb20 100644
--- a/sway/commands/workspace.c
+++ b/sway/commands/workspace.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <limits.h>
 #include <string.h>
diff --git a/sway/config.c b/sway/config.c
index e91c0c8b..568c8b53 100644
--- a/sway/config.c
+++ b/sway/config.c
@@ -1,3 +1,4 @@
+#undef _POSIX_C_SOURCE
 #define _XOPEN_SOURCE 700 // for realpath
 #include <stdio.h>
 #include <stdbool.h>
diff --git a/sway/config/bar.c b/sway/config/bar.c
index a8389244..908b2865 100644
--- a/sway/config/bar.c
+++ b/sway/config/bar.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <signal.h>
 #include <stdbool.h>
 #include <stdio.h>
diff --git a/sway/config/input.c b/sway/config/input.c
index 44c2be28..de3b21ed 100644
--- a/sway/config/input.c
+++ b/sway/config/input.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <limits.h>
 #include <float.h>
diff --git a/sway/config/output.c b/sway/config/output.c
index 54ebaa17..55779771 100644
--- a/sway/config/output.c
+++ b/sway/config/output.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <drm_fourcc.h>
 #include <stdbool.h>
diff --git a/sway/config/seat.c b/sway/config/seat.c
index 6d5d91ae..f2326189 100644
--- a/sway/config/seat.c
+++ b/sway/config/seat.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/sway/criteria.c b/sway/criteria.c
index 78ea8b8a..e16b4fa8 100644
--- a/sway/criteria.c
+++ b/sway/criteria.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdbool.h>
diff --git a/sway/desktop/launcher.c b/sway/desktop/launcher.c
index 0c02b997..28043d19 100644
--- a/sway/desktop/launcher.c
+++ b/sway/desktop/launcher.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <string.h>
 #include <wlr/types/wlr_xdg_activation_v1.h>
diff --git a/sway/desktop/output.c b/sway/desktop/output.c
index 81290ccb..600423bc 100644
--- a/sway/desktop/output.c
+++ b/sway/desktop/output.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <stdlib.h>
 #include <strings.h>
diff --git a/sway/desktop/transaction.c b/sway/desktop/transaction.c
index fd1c3d3a..042141ab 100644
--- a/sway/desktop/transaction.c
+++ b/sway/desktop/transaction.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/sway/desktop/xdg_shell.c b/sway/desktop/xdg_shell.c
index f4a25cf4..27a73f8a 100644
--- a/sway/desktop/xdg_shell.c
+++ b/sway/desktop/xdg_shell.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 199309L
 #include <float.h>
 #include <stdbool.h>
 #include <stdlib.h>
diff --git a/sway/desktop/xwayland.c b/sway/desktop/xwayland.c
index 9f3f4d5f..270cf08f 100644
--- a/sway/desktop/xwayland.c
+++ b/sway/desktop/xwayland.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 199309L
 #include <float.h>
 #include <stdbool.h>
 #include <stdlib.h>
diff --git a/sway/input/cursor.c b/sway/input/cursor.c
index b00f81a9..e8cd8112 100644
--- a/sway/input/cursor.c
+++ b/sway/input/cursor.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <math.h>
 #include <libevdev/libevdev.h>
diff --git a/sway/input/input-manager.c b/sway/input/input-manager.c
index c1bbdde0..9ee635af 100644
--- a/sway/input/input-manager.c
+++ b/sway/input/input-manager.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <stdio.h>
 #include <string.h>
diff --git a/sway/input/seat.c b/sway/input/seat.c
index 75fea484..9dd078c6 100644
--- a/sway/input/seat.c
+++ b/sway/input/seat.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <linux/input-event-codes.h>
 #include <string.h>
diff --git a/sway/input/seatop_default.c b/sway/input/seatop_default.c
index c56330fd..f2a9c2cd 100644
--- a/sway/input/seatop_default.c
+++ b/sway/input/seatop_default.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <float.h>
 #include <libevdev/libevdev.h>
 #include <wlr/types/wlr_cursor.h>
diff --git a/sway/input/seatop_down.c b/sway/input/seatop_down.c
index b4421fe6..12d7ae7a 100644
--- a/sway/input/seatop_down.c
+++ b/sway/input/seatop_down.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <float.h>
 #include <wlr/types/wlr_cursor.h>
 #include <wlr/types/wlr_tablet_v2.h>
diff --git a/sway/input/seatop_move_floating.c b/sway/input/seatop_move_floating.c
index 21d048ce..7de3f4d8 100644
--- a/sway/input/seatop_move_floating.c
+++ b/sway/input/seatop_move_floating.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <wlr/types/wlr_cursor.h>
 #include "sway/desktop/transaction.h"
 #include "sway/input/cursor.h"
diff --git a/sway/input/seatop_move_tiling.c b/sway/input/seatop_move_tiling.c
index 7de39ff6..4f4d6e41 100644
--- a/sway/input/seatop_move_tiling.c
+++ b/sway/input/seatop_move_tiling.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <limits.h>
 #include <wlr/types/wlr_cursor.h>
 #include <wlr/util/edges.h>
diff --git a/sway/input/seatop_resize_floating.c b/sway/input/seatop_resize_floating.c
index df683026..168dfffe 100644
--- a/sway/input/seatop_resize_floating.c
+++ b/sway/input/seatop_resize_floating.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <limits.h>
 #include <wlr/types/wlr_cursor.h>
 #include <wlr/types/wlr_xcursor_manager.h>
diff --git a/sway/input/seatop_resize_tiling.c b/sway/input/seatop_resize_tiling.c
index 869d11b5..9ce4ff8b 100644
--- a/sway/input/seatop_resize_tiling.c
+++ b/sway/input/seatop_resize_tiling.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <wlr/types/wlr_cursor.h>
 #include <wlr/util/edges.h>
 #include "sway/commands.h"
diff --git a/sway/input/tablet.c b/sway/input/tablet.c
index 902cb7ed..2863642a 100644
--- a/sway/input/tablet.c
+++ b/sway/input/tablet.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <wlr/config.h>
 #include <wlr/types/wlr_tablet_v2.h>
diff --git a/sway/ipc-server.c b/sway/ipc-server.c
index 9692a77f..7f353c0e 100644
--- a/sway/ipc-server.c
+++ b/sway/ipc-server.c
@@ -1,5 +1,4 @@
 // See https://i3wm.org/docs/ipc.html for protocol information
-#define _POSIX_C_SOURCE 200112L
 #include <linux/input-event-codes.h>
 #include <assert.h>
 #include <errno.h>
diff --git a/sway/lock.c b/sway/lock.c
index d267de4f..289e8ca4 100644
--- a/sway/lock.c
+++ b/sway/lock.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <wlr/types/wlr_scene.h>
 #include <wlr/types/wlr_session_lock_v1.h>
diff --git a/sway/main.c b/sway/main.c
index 73254dc2..1c4939aa 100644
--- a/sway/main.c
+++ b/sway/main.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <getopt.h>
 #include <pango/pangocairo.h>
 #include <signal.h>
diff --git a/sway/server.c b/sway/server.c
index 5b389f69..684b1dbd 100644
--- a/sway/server.c
+++ b/sway/server.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <stdbool.h>
 #include <stdlib.h>
diff --git a/sway/sway_text_node.c b/sway/sway_text_node.c
index 664db40e..5eba53ba 100644
--- a/sway/sway_text_node.c
+++ b/sway/sway_text_node.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <drm_fourcc.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/sway/swaynag.c b/sway/swaynag.c
index 6031174d..bc5e23ea 100644
--- a/sway/swaynag.c
+++ b/sway/swaynag.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <signal.h>
 #include <stdbool.h>
 #include <stdlib.h>
diff --git a/sway/tree/arrange.c b/sway/tree/arrange.c
index af925d05..d4003fe6 100644
--- a/sway/tree/arrange.c
+++ b/sway/tree/arrange.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <stdbool.h>
 #include <stdlib.h>
diff --git a/sway/tree/container.c b/sway/tree/container.c
index 78448090..9224b4fb 100644
--- a/sway/tree/container.c
+++ b/sway/tree/container.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <drm_fourcc.h>
 #include <stdint.h>
diff --git a/sway/tree/node.c b/sway/tree/node.c
index 213cf0a6..7aaf9762 100644
--- a/sway/tree/node.c
+++ b/sway/tree/node.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include "sway/output.h"
 #include "sway/server.h"
 #include "sway/tree/container.h"
diff --git a/sway/tree/output.c b/sway/tree/output.c
index cd7bf0c2..2d11195e 100644
--- a/sway/tree/output.c
+++ b/sway/tree/output.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <ctype.h>
 #include <string.h>
diff --git a/sway/tree/root.c b/sway/tree/root.c
index e9cea5e2..ae3c3cb2 100644
--- a/sway/tree/root.c
+++ b/sway/tree/root.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/sway/tree/view.c b/sway/tree/view.c
index 4a0d8069..35b4b73f 100644
--- a/sway/tree/view.c
+++ b/sway/tree/view.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <strings.h>
 #include <wayland-server-core.h>
diff --git a/sway/tree/workspace.c b/sway/tree/workspace.c
index 40d33435..a68dc927 100644
--- a/sway/tree/workspace.c
+++ b/sway/tree/workspace.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809
 #include <ctype.h>
 #include <limits.h>
 #include <stdbool.h>
diff --git a/swaybar/bar.c b/swaybar/bar.c
index 021fc3bd..5b1213a8 100644
--- a/swaybar/bar.c
+++ b/swaybar/bar.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/swaybar/config.c b/swaybar/config.c
index 5e828773..55bfcb72 100644
--- a/swaybar/config.c
+++ b/swaybar/config.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <string.h>
 #include "swaybar/config.h"
diff --git a/swaybar/i3bar.c b/swaybar/i3bar.c
index ccd5a076..62c22d43 100644
--- a/swaybar/i3bar.c
+++ b/swaybar/i3bar.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <json.h>
 #include <linux/input-event-codes.h>
 #include <ctype.h>
diff --git a/swaybar/ipc.c b/swaybar/ipc.c
index 33ae6544..03500bdf 100644
--- a/swaybar/ipc.c
+++ b/swaybar/ipc.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809
 #include <limits.h>
 #include <poll.h>
 #include <stdio.h>
diff --git a/swaybar/main.c b/swaybar/main.c
index a44c1e63..3dc67233 100644
--- a/swaybar/main.c
+++ b/swaybar/main.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/swaybar/render.c b/swaybar/render.c
index 1113ca44..879a4e42 100644
--- a/swaybar/render.c
+++ b/swaybar/render.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <linux/input-event-codes.h>
 #include <limits.h>
diff --git a/swaybar/status_line.c b/swaybar/status_line.c
index 2e9bb7f1..e542e606 100644
--- a/swaybar/status_line.c
+++ b/swaybar/status_line.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <assert.h>
 #include <fcntl.h>
 #include <sys/ioctl.h>
diff --git a/swaybar/tray/host.c b/swaybar/tray/host.c
index eea2caa5..79b54606 100644
--- a/swaybar/tray/host.c
+++ b/swaybar/tray/host.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/swaybar/tray/icon.c b/swaybar/tray/icon.c
index b513dca5..659edd86 100644
--- a/swaybar/tray/icon.c
+++ b/swaybar/tray/icon.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <ctype.h>
 #include <dirent.h>
 #include <stdbool.h>
diff --git a/swaybar/tray/item.c b/swaybar/tray/item.c
index d5fe50b1..ca6c03ad 100644
--- a/swaybar/tray/item.c
+++ b/swaybar/tray/item.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <arpa/inet.h>
 #include <cairo.h>
 #include <limits.h>
diff --git a/swaybar/tray/watcher.c b/swaybar/tray/watcher.c
index 2458a8c2..3cfea8d8 100644
--- a/swaybar/tray/watcher.c
+++ b/swaybar/tray/watcher.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdio.h>
diff --git a/swaymsg/main.c b/swaymsg/main.c
index db9346c4..573a7b16 100644
--- a/swaymsg/main.c
+++ b/swaymsg/main.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 
 #include <limits.h>
 #include <stdio.h>
diff --git a/swaynag/config.c b/swaynag/config.c
index cff3930f..efd71ce7 100644
--- a/swaynag/config.c
+++ b/swaynag/config.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <getopt.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/swaynag/main.c b/swaynag/main.c
index 20390207..634bddbf 100644
--- a/swaynag/main.c
+++ b/swaynag/main.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <signal.h>
 #include "log.h"
diff --git a/swaynag/swaynag.c b/swaynag/swaynag.c
index 6ea739e3..50eea148 100644
--- a/swaynag/swaynag.c
+++ b/swaynag/swaynag.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <assert.h>
 #include <sys/stat.h>
diff --git a/swaynag/types.c b/swaynag/types.c
index 409cc668..821e5b21 100644
--- a/swaynag/types.c
+++ b/swaynag/types.c
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <getopt.h>
 #include <stdbool.h>
 #include <stdlib.h>