Last Sunday

Write a script to list Last Sunday of every month in the given year.

#!/usr/bin/tclsh
#
# Write a script to list Last Sunday of every month in the given year.
#

proc lastDay {month year} {
    set days [clock format [clock scan "+1 month -1 day" \
        -base [clock scan "$month/01/$year"]] -format %d]
}

proc getLastSunday {baseDate} {
    set base [clock scan $baseDate -format "%Y%m%d"]
    set day_of_week [clock format $base -format %u]

    # Sunday may report as 0 or 7.
    # If 7, it is not necessary to adjust.
    if {$day_of_week != 7} {
       set timestamp [clock scan "12:00 last sunday" -base $base]
    } else {
       set timestamp $base
    }

    return [clock format $timestamp -format "%Y-%m-%d"]
}


if {$argc >= 1} {
    set year [lindex $argv 0]
} else {
    set year 2022
    puts "Set year to 2022."
}

for {set i 1} {$i <= 12} {incr i} {
    set lday [lastDay $i $year]
    set ltime [format %04d%02d%02d $year $i $lday]
    set sday [getLastSunday $ltime]
    puts $sday
}