Verification of clock time and time harmonization

Standard Operating Procedure for verification of clock time and time harmonization

1. Purpose

To provide a standard operating procedure for verification of clock time and time harmonization.

2. Scope

The scope of this SOP is applicable for verification of clock time and time harmonization of all GxP and non-GxP clocks used in the facility at [company name]. Following are covered under the scope of this SOP:

  • Computerized control systems
  • Equipment
  • Instruments such as weighing balance, Moisture IR balance, Friability tester, hardness tester etc.
  • Digital wall clocks
  • Server clocks
  • GPS clocks
  • Utility system clocks

3. Responsibility

User department: To verify the timings of the equipment, instrument, and other clocks covered under the scope of the SOP.

IT department: To support the site engineering department to harmonize the clock timings as per the master clock.

Engineering personnel: To maintain the list of clocks in the facility and to maintain the master clock used for time verification and harmonization.

4. Definitions

GPS: Global Positioning System (radio-navigation-system). By using this system, anyone can determine location, time, and velocity at any given point of time in any weather conditions throughout the world.

Server: It is a central computer with a program used to handle and control network resources.

5. Procedure

  1. The user department shall collect the master clock to verify the equipment and instrument clocks, and other clocks under the scope of this SOP. Before the use of a master clock to verify other clocks, the master clock must have to be verified for its accuracy. This verification shall be done as per the frequency defined in the procedure.
  2. Master clock shall be verified and adjusted with central server clock (connected with world clock) with the help of IT personnel on the day of verification of clocks. The Master clock shall have a unique identification number.
  3. Verification of the master clock shall be managed by the engineering department. The record shall be maintained for this verification and harmonization if any.
  4. After completion of master clock verification and time harmonization, hand over the clock to the user department for clock verification.
  5. User department shall verify the timing of departmental clocks and record for the same shall be maintained.
  6. In case of time difference observed more than 30 seconds, it shall be harmonized with the help of the engineering/ IT department. Record for the adjustment shall be maintained.
  7. Clock verification shall also be done in case of any maintenance done on the equipment where the clock is maintained and maintenance may have a potential impact on the computerized controls. For example, equipment PC, HMIs (Human Machine Interface), instruments, etc.
  8. After completion of maintenance activity, the system should be verified using the master clock by the engineering and user department.
  9. While verification of the above clocks if required, time harmonization may need to be done. The harmonization should be done as directed in the following table.
Noted Gap between the master clock and clock under verification Required action
Less than or equal to 30 secondsNo action required
31 seconds to 120 secondsTime adjustment as per master clock
More than 120 secondsNon-conformance and investigation to understand the impact of an occurrence.  Corrective Action and Preventive Actions to eliminate the root cause and other potential areas with similar possibilities.
  1. After completion of the clock verification activity, the master clock shall be re-verified against the central server timing.
  2. In case of difference observe more than 30 seconds from initial timing, the master clock shall be verified for replacement of battery or replacement of master clock itself depending on the case.
  3. In the above scenario, clock verification should be done once again.
  4. Replacement of the battery shall be documented to track the replacement frequency. Based on the trend data of battery replacement, the fixed frequency can be determined.
  5. After the battery replacement, the master clock should be kept under observation for 48 Hours. After 48 Hours, the difference of the master clock with respect to server timing should be verified. It should be no more than 30 Seconds. Record the observation. If it is found within the limit, the clock can be used for verification purposes.
  6. In case if the master clock does not meet the criteria of 30 seconds, it shall be retired from use and discarded. Record for destruction should be maintained.
  7. The server shall be synchronized using NTP (Network Time Protocol). Network Time Protocol is an Internet protocol used to synchronize the clocks of computers to reference clocks such as GPS.
  8. Network pools are connected as per
  9. The central server shall be connected to the all computers available site using the network system. Server shall be configured in such a way that all the commuters are connected to the network auto synchronize and the server is synchronizing with NTP.
  10. Clock timing shall be adjusted in the format, HH:MM: SS in 24 Hour format. In case of this format is not possible in any of the equipment/systems, it shall be adjusted as per the applicable setting for the clock.
  11. A list of the clock exempted from this standard operating procedure shall be documented.
  12. Any server synchronized digital Clocks, GPS clocks addition, or removal shall be done with the help of a change management system. The list of clocks shall be updated whenever addition or removal is done.

6. Frequency

  • Equipment, instrument and digital clocks (Non GPS) – Monthly
  • GPS clock, server connected clock and computerized systems – Six monthly
  • Master clocks used for verification – before and after verification of other clocks

7. Formats

  • Format for list of clocks
Sr. No.Clock Id.Area / LocationType of ClockVerification Frequency
  • Format for list of master clocks
Sr. No.Clock Id.Remark
  • Format for master clock verification

Clock Id.: _____________

Sr. No.DateDifference on verificationBattery changed (yes/ no)RemarkVerified by
  • Format for verification of clock

Master clock Id. Used for verification: ____________

Sr. No.DateClock Id. (Unit under verification)Difference on verificationAdjustment done (Yes/ No)RemarkVerified by
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