Okay so in the short term I've learned to live without DateAdd. I have solved most of my problems using addition within DateSerial. For example:
Code:
' previous method
SpringStart = DateSerial(Year(Date),1,1)
SummerStart = DateAdd("m",6,SpringStart)
...
' previous method in other code
DueDate = DateAdd("d",2,Date)
' current method
SpringStart = DateSerial(Year(Date),1,1)
SummerStart = DateSerial(Year(Date),7,1)
...
' current method in other code
DueDate=DateSerial(Year(Date),Month(Date),Day(Date) + 14)
It's not as elegant, I know. I especially mourn the loss of features like weekday or day of year in DateAdd. I will have to take my code apart to see what is wrong but at least I can keep things running this way.