How can I change the day of the monthly copies?

[alfema-esp]

Is it possible to change the date of the monthly backup so that it's performed at the beginning of the month?

I've seen that it's possible to modify a configuration file to change the backup time, but not to change the day of the month.

[ygerlach]

There is no intended ui / option for that.

I think you could modify an existing montly snapshot (edit its info.json and move it to the start of a month. The next snapshot should then be made a month later (if the computer is online to the specified time).
But i think this is not reliable nor desirable.

If you only want monthly snapshots (and not daily/weekly/ ...) you could modifiy the crontab entry of timeshift to only run on the first day of month.

[alfema-esp]

There is no intended ui / option for that.

I know, that's why I'm asking.

From what I've seen, the created parameter in info.json specifies the time of day the copy should be made, not the date.

I also make daily and weekly backups, so that won't work for me.

Thanks anyway for your reply.

[ygerlach]

From what I've seen, the created parameter in info.json specifies the time of day the copy should be made, not the date.

the created parameter contains the date and time, when the snapshot was made. The decision to create a new snapshot is based on that.

You can take the value from that and paste it into the date command to decode it:

date -d @1768413656
# Mi 14. Jan 19:00:56 CET 2026

So modifying the created value of an existing snapshot influences the date and time the next snapshot will be made.
You can use the date command to do the inverse operation as well:

date -d '2026-01-01 00:00' '+%s'
# 1767222000

See:

timeshift/src/Core/Snapshot.vala

Lines 216 to 220 in 8be5172

	string val = json_get_string(config,"created","");
	if (val.length > 0) {
	DateTime date_utc = new DateTime.from_unix_utc(int64.parse(val));
	date = date_utc.to_local();
	}

and:

timeshift/src/Core/Main.vala

Lines 1280 to 1282 in 8be5172

	else if (last_snapshot_monthly.date.compare(now.add_months(-1).add_minutes(1)) < 0){
	log_msg(_("Last monthly snapshot is more than 1 month old"));
	take_new = true;

[alfema-esp]

Thanks for your clarification. I had seen an explanation on a website about changing the start time, but it didn't mention the date, so I thought it couldn't be changed.

I changed the parameter in both monthly info.json files, both the snapshots directory and the snapshots-monthly directory, to January 1st. This month, the backup was scheduled for the 23rd, so I suppose it shouldn't be until early February.

[alfema-esp]

ygerlach, thank you very much, the new monthly backup was performed on the 1st at 00:00:01, exactly on schedule. I happened to have my computer on at that time; I suppose if it hadn't been, it would have been performed later, when I turned the computer on again.

Greetings.