Incorrect Date Calculation When Adding One Month with AddMonths Function

January 30, 2028 + 1 month would normally be February 30, 2028. However, February 2028 is a leap year (2028 is divisible by 4), so February has 29 days. Since February 30 doesn’t exist, the date rolls back to February 29, 2028. So, the final date is 29th February 2028.

function test()
{
    var mydate = aqDateTime.SetDateElements(2028, 1, 30);
    var date = aqConvert.DateTimeToFormatStr(mydate, "%d/%m/%Y");
    Log.Message(date);
    var newdate = aqDateTime.AddMonths(date, 1);
    Log.Message(newdate);    
}

This is expected behaviour for most date/time libraries including those based on .NET, Java, Python, and TestComplete as well.

If you add days instead, then you will get March 1, 2028

function test()
{
    var mydate = aqDateTime.SetDateElements(2028, 1, 30);
    var date = aqConvert.DateTimeToFormatStr(mydate, "%d/%m/%Y");
    Log.Message(date);
    var newdate = aqDateTime.AddDays(date, 31);
    Log.Message(newdate);    
}

This is referred to as "function as designed".