Help with calculating in a control... please

[DevArrah]

I'm having a problem with a control in access 2000.

I have two textboxes on a form called start and length
In the controlSource of a third textbox I have =[start]+Year[length]
The problem is when I enter data into the field I get nutty results.
After literal hours tooling around with I finally tried setting the
controlSource to =Year([length])

Then when I played with the form get these results (result as number
formatted as a general number)

entered into length Result
0 1899
1 1900
2 1900
3 1900

All i want to do is to have a text that automatically adds 'length'
years to the start date. What on god's green earth am I doing wrong? Any
semi-logical reason why I get the results that I do?

I admit this is the first time I'm i've done any extensive fooling
around in access but for the life of me I don't understand why the same
calculation works in a query but not in the control.

 

[Allen Browne]

Assuming that Start is a Date/Time field, and Length is a Number field, use
the DateAdd() function to add the number years to the date, i.e.:
DateAdd("yyyy", [length], [start])

To explain the results you got, internally Access stores date/time values as
a number where the whole number represents the date and the fraction the
time (0.5 = noon (half a day), 0.25 = 6am, etc). They decided that day zero
would be Dec 30 1899. Therefore:
Year(0)
calculates as 1899, and so does Year(1) since that's the next day. Year(2)
is the first day of 1900, so following days up to 366 are all in 1900.

HTH