Hi Community,

If I have a tag which updates every 2 hours and want to know its yesterday's value. The equation **tagvalue('tag1','*-1d')** won't do because the data updates only once in 2 hours and its calculation will be based on the PI system clock (since * indicates now) and not on tag's timestamp. For example, the latest data is** 25Mar2014 18:00**, the timestamp of my equation should be** 24Mar2014 18:00.**

Any help will be appreciated!

TIA :)

_{Hey TIA,}_{You could use the following equation if you'd like:}_{PrevEvent('TagValue', '*-23h')}_{This would assure you that you get the previous value from the archive at a time 23 ago (hence if your data updates every two hours, it will grab the one 24 hours ago).}_{Does this work for you?}_{-Charlie}