Split holiday code into its own file

dotlib/generic-post/calendar.sh

@@ -0,0 +1,32 @@
+calendar-determine-holiday() {
+  local month day
+  read -r month day < <(date "+%m %d")
+
+  if (( 10#$month == 3 && 10#$day < 18 )); then
+    if (( 17 - 10#$day == 0 )); then
+      printf "Happy Saint Patrick's day!\n"
+    else
+      printf "Only %d days left until Saint Patrick's day!\n" "$(( 17 - 10#$day ))"
+    fi
+
+    PS1_prompt_sym=🍀
+  elif (( 10#$month == 10 )); then
+    if (( 31 - 10#$day == 0 )); then
+      printf 'Have a spooky halloween!\n'
+    else
+      printf 'Only %d days left until Halloween!\n' "$(( 31 - 10#$day ))"
+    fi
+
+    PS1_prompt_sym=🎃
+  elif (( 10#$month == 12 && 10#$day < 26 )); then
+    if (( 25 - 10#$day == 0 )); then
+      printf 'Merry Christmas!\n'
+    else
+      printf 'Only %d days left until Christmas!\n' "$(( 25 - 10#$day ))"
+    fi
+
+    PS1_prompt_sym=🌲
+  fi
+}
+
+calendar-determine-holiday