DateSerial not working

[tagteam]

I am trying to get the first day of the month after the average of a group of dates. I am able to accurately get the Average Date. Then I use an unbound field to get the year by using Year([avgdate]) and get the month by Month([avgdate]) and those both work and I get the correct year and month.

However, when I use =DateSerial([AvgYear],[AvgMonth],1) it doesn't work.

For example, if I have an average date of 1/8/2025 in AvgYear I get 2025 and in AvgMonth I get 1. I try to use DateSerial to get 1/1/2025 so I can then just add 1 month but I get 12/1/1899

[Welshgasman]

yy=2025
mm=1
? dateserial(yy,mm,1)
01/01/2025 
dt=#01/08/2025#
? year(dt)
 2025 
? month(dt)
 1 
? dateserial(year(dt),month(dt),1)
01/01/2025

[tagteam]

Sorry, for some reason I accidentally had this in the Default Value and it would not work. When I moved the above the the ControlSource it worked fine.

using =Year([AverageDOA]) to get year and =Month([AverageDOA])+1 to get month and =DateSerial([AvgYear],[AVGMonth],1) to get new date