calculating complete quarters between two dates

Hi,

I need to write a function to calculate the number of complete quarters
between two given dates.

As the calculations are based on tax rules, they must be actual
calender months - not approximations.

Therefore, something, assuming I run the POSTed values through
'mktime', an instruction like:

$months = ceil((($end_date - $start_date) / 60 / 60 / 24 / 365.25 *
12))

would give an approximation. However, in some instances where there are
28 or 30 days in a month, it may not give the correct answer.

I've had a look in the PHP documentation, but there appears to be no
inbuilt functions to handle this. Can any correct me on this if I am
wrong ?

Otherwise, I guess the only way would be to use lots of conditional
logic, working out whether the difference between the start month and
end month, then if end date is higher than the start date, etc...

If anyone has done something similar, please let me know.

Rgds
Neil.

You might use floor((date("m",$time)-1)/4)+1 for getting the quarter
based on months. A function like

function qsincey0($time) {
return date("Y",$time)*floor((date("m",$time)-1)/4);
}

Would return the number of quarters since year 0

$qdiff = qsincey0($date2)-qsincey0($date1)

Would give the difference (0 for the dates being in the same quarter)
If you would want the dates 1-Jan-2006 and 31-Mar-2006 give '1 quarter
difference' instead of 0 (for being in the same quarter), you may consider:

$qdiff = qsincey0(strtotime("-1 day",$date2))-qsincey0(strtotime("+1
day"),$date1) - 1;

Which brings those particular dates outside the quarter, giving a
'quarter difference' of 2, leaving 1 to substract.

Regards,
Karel

neil@invidion.co.uk wrote:
> Hi,
>
> I need to write a function to calculate the number of complete quarters
> between two given dates.
>
> As the calculations are based on tax rules, they must be actual
> calender months - not approximations.
>
> Therefore, something, assuming I run the POSTed values through
> 'mktime', an instruction like:
>
> $months = ceil((($end_date - $start_date) / 60 / 60 / 24 / 365.25 *
> 12))
>
> would give an approximation. However, in some instances where there are
> 28 or 30 days in a month, it may not give the correct answer.
>
> I've had a look in the PHP documentation, but there appears to be no
> inbuilt functions to handle this. Can any correct me on this if I am
> wrong ?
>
> Otherwise, I guess the only way would be to use lots of conditional
> logic, working out whether the difference between the start month and
> end month, then if end date is higher than the start date, etc...
>
> If anyone has done something similar, please let me know.
>
> Rgds
> Neil.
>

Ummm

Taxed based quarters in the USoA start ( and stop ) on known days of
the year.

Can't you compare for this?
1st quarter - 1/1/year
2nd quarter - 1/4/year
3rd quarter - 1/7/year
4th quarter - 1/10/year

If your date is >= 1st AND < 3rd, wouldn't that hold 2 complete
quarters?

todh