TIME+ Technical Bulletin - Daylight Saving.

The TimeClocks on a TIME+ system keep their own internal time and date values, they are synchronised according to the host system's time and date values which are sent regularly – usually once a day just after midnight. TimeClocks also request and verify the correct time and date whenever they are reset. In order to set the correct time due to a daylight saving scheme it is necessary to do two things:

1. Ensure that the host system's time is changed at the correct time and date to the new value.
2. Ensure that the TimeClocks are sent the time once the new value has been set.

An alternative is to set the system time to the new value prior to the regular midnight timeload - for some it may be ok to do this last thing on Friday. The procedures and options to achieve this are set out below:

1. Automatic Time Change Program:

The Automatic Time Change program (TA114 option 4 on the Configure Time Clocks menu) automates daylight saving changes at the correct time. It will attempt to change the system time and date using SET-TIME and SET-DATE verbs – these will deliberately fail on non-native systems such as UNIX. However the program may still be used to ensure that the new time is sent to the TimeClocks at the right moment.

TA114    Automatic Time Change                 17 MAR 00

.

 1)  Date to be changed            26MAR00

 2)  Time to be changed            01:00:00

 3)  Change to Date                26MAR00

 4)  Change to Time                02:00:00

 5)  Changed time

 6)  Date To be changed            29OCT00

 7)  Time to be changed            02:00:00

 8)  Change to Date                29OCT00

 9)  Change to Time                01:00:00

10)  Changed time

  To register changes at Time Clocks

  Their port must be re-started  

To take effect entry 5 or 10 should be set to null (enter a single space). A simple way to achieve this and load relevant defaults is to use the Delete option, re-enter the program from the menu and hit return through all entries to take the new defaults for the next BST/GMT changes. Once TA100 (the TimeClock comms program) has done the Clock Change then the relevant Changed Time in entry 5 or 10 is set to the actual time once the change is made. This will only be done if at least one TimeClock Port is running TA100 on the Date to be changed and runs through the Time to be changed. TA100 will automatically re-start on all logged-on ports; this will then cause a Timeload of the new system time to all live TimeClocks. Obviously the TimeClock ports must be logged on prior to the change time for this to work!

2. UNIX based systems: Unix based systems

(uniVerse, UniData, Reality, Sequoia etc) do not have a SET-TIME or SET-DATE Tcl verb - however these systems normally have automatic time-zone & daylight saving changes which can be configured when the operating system is installed (please check with your operating system vendor as to whether this has been done). This is normally apparent by the system time being reported as HH:MM GMT/BST or a time zone, which you recognise. If, however, your system time is reported in an unusual or default time zone (e.g. Pacific or Eastern Std time for European sites) your system may not have been configured correctly. In either case- even though TA114 does not automatically set the system time it will reset the TimeClock ports and so do a Timeload at the right moment. UNIX users - see your on-line manual pages for "timezone" etc or ask for the TIME+ technical Bulletin unix_tz.doc. The timezone variable should be set in advance of the change date. However it is also essential that the TimeClock ports are stopped and that you log off all TIME+ users including yourself before globally setting the timezone environment variable (via the recommended system admin procedure), logging off, and only then logging back on and starting the TimeClock ports. If you intend to do the change of time manually make sure that the timezone setting is not set and beware that many UNIX vendors advise that manual system time/date changes be done in single user mode.

3. Native Pick systems:

Native Pick users beware - please check that TA114 is not set do an automatic change if you intend to do the change manually - otherwise you will get a double time change!

4. TimeClock firmware 3.56 and later:

TimeClock firmware version 3.56 and later always requests a Timeload at 02:00am. So systems where all TimeClocks have this version or later do not need to use TA114. The version number is displayed at the TimeClock when it resets and is also shown in both the Status Display (TA103) in response to a Status Request and the Status From TimeClocks Report (TA117).

5. UK daylight saving date sometimes differs from US default scheme:

BEWARE: when the Sunday of the fifth week is the last day of the month the default rules may not apply to the UK, check with the Home Office (A Div. on 0171 273 3193) or Whittakers Almanac.

The dates for the next two years are: 2000 March 26th , October 29th , 2001 March 25th, October 28th.

6. PC based systems:

PC based system users please check that the BIOS does not have any daylight saving scheme enabled, otherwise you may get a double time change if you use one of these time changing schemes!

7. Systems with Radio Clock Interface

The Radio Clock interface is usually configured to reset the system time at pre-determined intervals – this should over-ride any other means of setting the clock. However you might still wish to disable the adjustment of daylight saving time by such schemes as the UNIX Timezone setting – just retain the setting of the GMT/BST legend.

If you require further information or assistance please contact Clear Systems at the address below or email us at Service@ClearSystems.co.uk