i want to thank you for all your help. i did make a small change to your code:

TimeStamp calcDiff(TimeStamp now, const TimeStamp &future)

{

byte current_month = now.mm;

unsigned long sec_now = now.ss + ((unsigned long)now.min * 60) + ((unsigned long)now.hh * 3600);

unsigned long sec_future = future.ss + ((unsigned long)future.min * 60) + ((unsigned long)future.hh * 3600);

if (sec_future < sec_now)

{

sec_future += 86400;

++now.dd;

}

if (future.dd < now.dd)

{

now.dd = DAYS_IN_MONTH[now.mm-1] - now.dd + future.dd;

++now.mm;

} else {

now.dd = future.dd - now.dd;

}

if (future.mm < now.mm)

{

now.mm = future.mm + 12 - now.mm;

if ((current_month + now.mm) > 12){

now.dd -= (DAYS_IN_MONTH[current_month-1] - DAYS_IN_MONTH[(current_month + now.mm - 12)-1]);

}else{

now.dd -= (DAYS_IN_MONTH[current_month-1] - DAYS_IN_MONTH[(current_month + now.mm)-1]);

}

++now.yy;

} else {

now.mm = future.mm - now.mm;

}

sec_now = sec_future - sec_now;

now.yy = future.yy - now.yy;

now.hh = sec_now / 3600;

now.min = (sec_now - ((unsigned long)now.hh * 3600)) / 60;

now.ss = sec_now % 60;

return now;

}

the changes were made when the remaining months were being calculated, and if future.mm < now.mm, some adjustments to the days needs to be done.

here is the resulting output from your code after some tests:

Current Time/Date: - 8 / 18 / 2013 : - 18 : 3 : 0

Time Until 1 / 10 / 2014 : - 0 : 0 : 0

0 years, 4 month, 22 days

5 hours, 57 minutes, 0 seconds

Current Time/Date: - 8 / 18 / 2013 : - 18 : 3 : 0

Time Until 1 / 10 / 2014 : - 20 : 0 : 0

0 years, 4 month, 23 days

1 hours, 57 minutes, 0 seconds

Current Time/Date: - 8 / 18 / 2013 : - 18 : 3 : 0

Time Until 1 / 20 / 2014 : - 0 : 0 : 0

0 years, 5 month, 1 days

5 hours, 57 minutes, 0 seconds

Current Time/Date: - 8 / 18 / 2013 : - 18 : 3 : 0

Time Until 1 / 20 / 2014 : - 20 : 0 : 0

0 years, 5 month, 2 days

1 hours, 57 minutes, 0 seconds

Current Time/Date: - 8 / 18 / 2013 : - 18 : 3 : 0

Time Until 2 / 10 / 2014 : - 0 : 0 : 0

0 years, 5 month, 22 days

5 hours, 57 minutes, 0 seconds

Current Time/Date: - 2 / 18 / 2013 : - 18 : 3 : 0

Time Until 3 / 10 / 2014 : - 0 : 0 : 0

1 years, 0 month, 19 days

5 hours, 57 minutes, 0 seconds

thanks again for your help, and reminding me of the beauty of using "struct" to create a more easy to use variable structure.