There are two cases in which utc.add function is giving incorrect result-
Case 1-
Consider,
i.date = 1 December 2008,
hold.mfsh = 23,
plst.stdt is reference variable.

The utc.add function was written like this-
utc.add (i.date,
0,
-1 * hold.mfsh,
0,
0,
0,
0,
plst.stdt)


After utc.add function is executed plst.stdt comes as 1 January 2006 which is incorrect.
It should come as 1 February 2007.

Case 2-
Consider,
i.date = 1 December 2008,
hold.mfsh = 24,
plst.stdt is reference variable.

The utc.add function was written like this-
hold.mfsh = hold.mfsh - 1
e = utc.add(i.date,
0,
-1 * hold.mfsh,
0,
0,
0,
0,
temp.date)

e = utc.add (temp.date,
0,
-1,
0,
0,
0,
0,
plst.stdt)

here temp.date is temporary variable
After utc.add function is executed plst.stdt comes as 1 January 2005 which is incorrect.
It should come as 1 January 2007.

Does anbody knows why this problem is coming and how to solve this?

Thanks and Regards,
Pankhuri

Here some examples extracted form Programmers Guide

Example

This example shows the addition of days and hours across winter/summertime change

in_utc = date.to.utc(2002,3,29,13,30,0)

res = utc.add( in_utc, 0, 0, 1, 24, 0, 0, ou_utc )
The result in timezone "Europe/Amsterdam" is: ou_utc=1017577800, res = 0 (that is 2002.3.31 14:30:00)

This example shows the addition of days across winter/summertime change

in_utc = date.to.utc(2002,3,29,13,30,0)

res = utc.add( in_utc, 0, 0, 2, 0, 0, 0, ou_utc )
The result in timezone "Europe/Amsterdam" is: ou_utc=1017574200, res = 0 (that is 2002.3.31 13:30:00)

This example shows the substraction of 1 month from March 31st, 2000.

in_utc = date.to.utc(2000,3,31,9,0,0)

res = utc.add( in_utc, 0, -1, 0, 0, 0, 0, ou_utc )
The result in timezone "Europe/Amsterdam" is: ou_utc=951811200, res = 1 (that is 2000.2.29 9:0:0)

As you can see there are no examples with more then 12 months.

Guess in this situation you should convert 12 months to 1 year.

here worked well.

regards.