clock read-calendar is a Cisco IOS privileged EXEC command that synchronizes the software clock to the hardware calendar. It performs a one-time synchronization; it does not keep both time sources synchronized automatically. section 2.1.2
Use the command when the hardware calendar contains the desired date and time:
- Run clock read-calendar from privileged EXEC mode. section 2.1.2
- Verify the resulting software time with show clock or show clock detail. section 2.1.2
- Repeat the command whenever another one-time synchronization is required; use NTP for automatic network synchronization. section 2.1.2 section 2.4
R1# show clock detail *08:56:18.831 UTC Mon Aug 28 2023 #1 Time source is hardware calendar #2 #1 The asterisk (*) indicates that the time is not authoritative. #2 R1 learned the date and time from its hardware calendar.
Use show clock detail to inspect the software clock and identify whether its time source is the hardware calendar. section 2.1.2
