Forum OpenACS Q&A: how to find out the exact date of i.e. "1st monday of this month"

Cheers

set datenow [clock scan [date]]
set first_day_of_month "[clock scan [clock format $datenow -format %Y]-[clock format $datenow -format %m]-01]"
set day_of_year [clock format $first_day_of_month -format %j]
set day_of_week_of_first_day [clock format $first_day_of_month -format %w]

So you'll now have the day of year of the first day of the current month as well as it's day of week. Sunday is 0.

With those two values, a couple or so [expr]'s should get you the first monday.

Also possible using a similar approach in sql.

Thanks

It only works because of the ports of the oracle functions.  See my previous post on where those functions were defined.

The next_day function port for PG converts the weekday to int. So if you'd want to use 1, then I guess rewrite the function and support both a weekday and an int.

I found out about a convenient way to calculate i.e. the 4 Monday of this or next month:

set datenow                            [clock scan now]
set first_day_of_month                  [clock scan [clock format $datenow -format %Y]-[clock format $datenow -format %m]-01]
set first_day_of_month_fmt              [clock format $first_day_of_month -format "%Y-%m-%d"]
set first_day_of_next_month            [clock scan "1 month" -base [clock scan $first_day_of_month_fmt]]
set first_day_of_next_month_fmt        [clock format $first_day_of_next_month -format "%Y-%m-%d"]

set n_day_of_n_week_of_month            [clock scan "Monday 3 Week" -base [clock scan "$first_day_of_month_fmt"]]
set n_day_of_n_week_of_month_fmt        [clock format $n_day_of_n_week_of_month -format "%Y-%m-%d"]
set n_day_of_n_week_of_next_month      [clock scan "Monday 3 Week" -base [clock scan "$first_day_of_next_month_fmt"]]
set n_day_of_n_week_of_next_month_fmt  [clock format $n_day_of_n_week_of_next_month -format "%Y-%m-%d"]

http://pleac.sourceforge.net/pleac_tcl/datesandtimes.html

You can also calculate how many weeks, days, hours, minutes, seconds an event is away...