How to get accurate backup end time when it is taken from synchronous standby ?

Greetings,

When we take backups from a synchronous standby replica, how can we get the accurate timestamp of the backup end time ? (As backup history files are not generated on standbys)
For example:
this is a part of control file after a backup (created using wal-g by calling pg_startbackup and pg_stopbackup),
Fake LSN counter for unlogged rels: 0/3E8
Minimum recovery ending location: 28/28000B68
Min recovery ending loc's timeline: 2
Backup start location: 0/0
Backup end location: 0/0
End-of-backup record required: no
here I can see that minimum recovery ending location as LSN value, how can we get the timestamp of it ?
The backup label file looks like this.
INFO: 2022/07/26 23:25:23.850621 ------------ LABLE FILE START ----------
INFO: 2022/07/26 23:25:23.850628 START WAL LOCATION: 1D/F94C7320 (file 000000020000001D000000F9)
INFO: 2022/07/26 23:25:23.850633 CHECKPOINT LOCATION: 1E/EDA8700
INFO: 2022/07/26 23:25:23.850639 BACKUP METHOD: streamed
INFO: 2022/07/26 23:25:23.850645 BACKUP FROM: standby
INFO: 2022/07/26 23:25:23.850653 START TIME: 2022-07-26 23:10:27 GMT
INFO: 2022/07/26 23:25:23.850659 LABEL: 2022-07-26 23:10:27.545378 +0000 UTC m=+0.167723956
INFO: 2022/07/26 23:25:23.850665 START TIMELINE: 2
INFO: 2022/07/26 23:25:23.850669
INFO: 2022/07/26 23:25:23.850676 ------------ LABLE FILE END ----------

How can we do PITR using timestamp if we don’t know the accurate timestamp of minimum recovery point ?

Thanks.
Best,
Harinath