Applies To:
  • CitectSCADA 4.x

What happens to the time saved in Trend History files when daylight saving comes into effect. 

Citect keeps track of time in UCT (Universal Coordinate Time, which is exactly the same time all around the world and does not change during daylight savings). When a time is displayed on the screen it is converted to local time depending on the set time zone and if daylight saving is in effect. The time saved in the Trend History files is the Citect UCT time. When a trend is displayed the same conversion is done depending on the set time zone and daylight saving. When the time zone information on a computer is changed to daylight it has no effect on the trend history files as the time is saved in UCT time. So when you go from normal Time to Daylight Time the time saved in the Trend File is the same but when it is displayed it is converted to be one hour ahead to make it in daylight savings.