Add option --date=FORMAT to specify the date part in the snapshot name.

src/zfs-auto-snapshot.8

@@ -16,6 +16,9 @@ for those in which the user-property \fBcom.sun:auto-snapshot\fR is
 set to \fBfalse\fR.  This option reverses the behavior and requires
 \fBcom.sun:auto-snapshot\fR to be set to \fBtrue\fR.
 .TP
+\fB\-D\fR, \fB\-\-date=\fIFORMAT\fR
+Use \fIformat\fR for snapshot name. See \fBdate\fR(1) for more information.
+.TP
 \fB\-d\fR, \fB\-\-debug\fR
 Print debugging messages.
 .TP

src/zfs-auto-snapshot.sh

@@ -24,6 +24,7 @@ IFS="
 "
 
 # Set default program options.
+opt_date_format='%F-%H%M'
 opt_backup_full=''
 opt_backup_incremental=''
 opt_default_exclude=''
@@ -56,6 +57,7 @@ print_usage ()
 {
 	echo "Usage: $0 [options] [-l label] <'//' | name [name...]>
   --default-exclude  Exclude datasets if com.sun:auto-snapshot is unset.
+  -D, --date=FORMAT  Date format. Default '%F-%H%M'.
   -d, --debug        Print debugging messages.
   -e, --event=EVENT  Set the com.sun:auto-snapshot-desc property to EVENT.
       --fast         Use a faster zfs list invocation.
@@ -210,9 +212,9 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 GETOPT=$(getopt \
   --longoptions=default-exclude,dry-run,fast,skip-scrub,recursive \
   --longoptions=event:,keep:,label:,prefix:,sep: \
-  --longoptions=debug,help,quiet,syslog,verbose \
+  --longoptions=date:,debug,help,quiet,syslog,verbose \
   --longoptions=pre-snapshot:,post-snapshot:,destroy-only \
-  --options=dnshe:l:k:p:rs:qgv \
+  --options=D:dnshe:l:k:p:rs:qgv \
   -- "$@" ) \
   || exit 128
 
@@ -221,6 +223,10 @@ eval set -- "$GETOPT"
 while [ "$#" -gt '0' ]
 do
 	case "$1" in
+		(-D|--date)
+			opt_date_format="$2"
+			shift 2
+			;;
 		(-d|--debug)
 			opt_debug='1'
 			opt_quiet=''
@@ -530,7 +536,7 @@ SNAPPROP="-o com.sun:auto-snapshot-desc='$opt_event'"
 
 # ISO style date; fifteen characters: YYYY-MM-DD-HHMM
 # On Solaris %H%M expands to 12h34.
-DATE=$(date --utc +%F-%H%M)
+DATE=$(date --utc +"$opt_date_format")
 
 # The snapshot name after the @ symbol.
 SNAPNAME="$opt_prefix${opt_label:+$opt_sep$opt_label}-$DATE"