diff --git a/.bauke/Restic Backups.md b/.bauke/Restic Backups.md
index e9999ab..b486df1 100644
--- a/.bauke/Restic Backups.md
+++ b/.bauke/Restic Backups.md
@@ -44,7 +44,7 @@ restic-b2 check
* Monthly music library backup:
```zsh
-restic-b2 backup --tag "$(date -d "$(date +'%Y-%m-01') -1 day" +'%B %Y')" ~/Beets
+restic-b2 backup --tag "$(date-last-month-year)" ~/Beets
```
* KeePassXC database:
diff --git a/.functions.zsh b/.functions.zsh
index 7f360af..3571936 100644
--- a/.functions.zsh
+++ b/.functions.zsh
@@ -1,3 +1,12 @@
+# Returns the previous month as "Month Year" (ie. "April 2023").
+# date-last-month-year
+date-last-month-year () {
+ # The inner date "+'%Y-%m-01'" gets the date of the current month with 01 as the day.
+ # Then that date has 1 day subtracted (date -d ... -1 day).
+ # And finally "+'%B %Y'" gets the resulting date as the month and year.
+ date -d "$(date +'%Y-%m-01') -1 day" +'%B %Y'
+}
+
# Copies a section from a video using ffmpeg.
# extract-clip