Custom btrfs snapshots for when you need different naming schemes than timeshift or snapper and keep them for 1 month

snapshot_take

#!/bin/bash
TIMESTAMP=`date +"%Y.%m.%d-%H.%M.%S"`
SNAP="btrfs subvolume snapshot -r"
SOURCE_DIR="/Tank/data"
SNAP_DIR="/Tank/data/.snapshots"
SNAP_NAME="@GMT_$TIMESTAMP"

$SNAP $SOURCE_DIR $SNAP_DIR/$SNAP_NAME
rm -rf $SNAP_DIR/.snapshots/@SNAP_NAME/.snapshots/*

# Cleanup old snapshots
for D in `find "$SNAP_DIR/" -maxdepth 1 -type d`
do
    # If the folder is not the parent folder
    if [[ "$D" != "$SNAP_DIR/" ]]
    then
        CREATED=$(btrfs subvolume show $D | grep -oP 'Creation time:\s*\K\d.*$' | perl -pe "s/(\d{4}-\d{2}-\d{2}).+/\1/")
        TIMELINE=$((($(date +%s)-$(date +%s --date "$CREATED"))/(3600*24)))

        # If the snapshot is older than 1 month
        if [[ $TIMELINE > 31 ]]
        then
            echo snapshot $D is $TIMELINE days old, deleting
            btrfs sub delete "$D"
        fi
    fi
done