You need to define a 7 element DINT array with the tagname DateTime (you can call it what you want, I call it DateTime)
Then using a GSV instruction set the class name to WallClockTime, Attribute to LocalDateTime, and Destination is DateTime[0]
GSV WallClockTime,,LocalDateTime,DateTime[0]
DateTime[0] will be the year,
DateTime[1] will be the month,
DateTime[2] will be the date,
DateTime[3] will be the hour in 24hr format
DateTime[4] will be the minute
DateTime[5] will be the second
DateTime[6] will be microseconds
Now using compare or LIM instructions you can create a rung to turn on the valve.
Example
BST EQU DateTime[3] 7 NXB EQU DateTime[3] 19 BND OTE SolnValve
Will turn on the solenoid valve when the hour is 7:00am and 7:00pm