# Setting the System Clock Manually

Before you set the system clock, obtain the following information about your time zone:

- The name of the time zone
- The difference (offset) between the time zone and UTC
- The dates and times of transitions to and from summer time (daylight saving time)
- The difference between the standard time and summer time (daylight saving time)

The international website www.timeanddate.com contains information about time zones.

| Note: Be sure to set the time zone (default is UTC) and summer time dates before you set the clock.

You can set the system clock at any time. This process involves the following steps:

1. Set the time zone.
2. Set the summer time dates.
3. Set the time.
4. Check the clock settings.

clock set

- Use to set the time and date on your system manually.
- Use the following syntax for setting the time: HH:MM:SS. This is the current time in 24-hour format—hours:minutes:seconds.
- There are two acceptable date forms for this command. Both produce the same display when you run the show clock command.
  - Day:month:year
  - Month:day:year
- Examples
  host1#clock set 08:12:42 12 March 2000 host1#clock set 11:12:55 March 10 2000
- There is no no version.
- See clock set.

clock summer-time date

- Use to set the clock to switch automatically to summer time (daylight saving time).
- Example
  host1(config)#clock summer-time PDT date 1 April 200X 2:00
  31 October 200X 2:00 60
- Use the no version to prevent automatic switching to summer time.
- See clock summer-time date.

clock summer-time recurring

- Use to set the clock to summer time at the same time each year.
- Example—This overrides the default settings for PDT,
  host1(config)#clock summer-time PDT recurring first Sunday April 2:00 last Sunday October 2:00
- Use the no version to prevent automatic switching to summer time.
- See clock summer-time recurring.

clock timezone

- Use to set the time zone for display.
- Example—This sets the time zone to 5 hours behind UTC.
  host1(config)#clock timezone EST -5
- Use the no version to set the time zone to UTC, the default setting.
- See clock timezone.

show calendar

- Use to display the real-time clock hardware time and date.
- Appropriate error messages are displayed for a real-time clock that is malfunctioning. Setting the software clock using the clock set command also causes the hardware or real-time clock chip to be updated to the same time as the software system clock.
- Example 1—Shows the real-time clock hardware time and date when the real-time clock chip is working correctly

      host1#show calendar
      MON JUN 06 2011 14:55:09 UTC

- Example 2—Shows the state of the real-time clock battery when it has encountered a failure

      host1#show calendar
      "RTC battery failed!"

- See show calendar.

show clock

- Use to display the system time and the date.
- Example 1—Shows time source value when clock is manually configured

      host1#show clock detail
      TUE JAN 23 2007 11:50:47 UTC
      time source: manually entered by user
      timezone: UTC (0 minutes from UTC)

- Example 2—Shows time source value when clock is synchronized with NTP

      host1#show clock detail
      TUE JAN 23 2007 11:50:47 UTC
      time source: Configured via NTP
      timezone: UTC (0 minutes from UTC)

- See show clock.