regarding zenon logic

regarding zenon logic

sir,
i need to develop a logic move a variable according to the requirement.
im calcuating the per day power of a plant and it is moved to # varDay01. After the day changes (suppose from day 01 to day 02),
the total value calculated must move to #var01
ie ;  var01 :=varDay01

when day change from day 02 to day 03
per day power in #varDay02 moves to  #var01 and
value in the varDay01 moves to var02

when day change from day 03 to day 04
per day power in #varDay03 moves to  #var01 and
value in the varDay02 moves to var03