Calculates day of the week for a givien date - Mikrotik Script
How To Calculates day of the week for a givien date on RouterOS

# Calculates day of the week for a givien date
# Month: jan,feb ... nov,dec   (must be lower-case)
# Day: 1 - 31
# Year: 1583 - ...
# mmm/dd/yyyy   same format as [/system clock get date]
# (ex. feb/19/2012)
# by melboyscout (melboyscout [at] gmail.com)

:local date [/system clock get date]

# Math Calculation here
:local result ""
:local months [:toarray "jan,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec"]
:local daytbl [:toarray "sun,mon,tue,wed,thu,fri,sat"]

:local month [:pick $date 0 3]
:local day [:pick $date 4 6]
:local dayc [:pick $date 5 6]
:local year [:pick $date 7 11]

# if the first char is a 0 (zero) only read last char, else script fails
:if ([:pick $date 4 5] = 0) do={ :set day ($dayc)}

:local sum 0
:local aaa 0
:local yyy 0
:local mmm 0
:local nmonth 1

:for mindex from=0 to=[:len $months] do={
  :if ([:pick $months $mindex] = $month) do={:set nmonth ($mindex + 1) }
}

:set aaa ((14 - $nmonth) / 12)
:set yyy ($year - $aaa)
:set mmm ($nmonth + 12 * $aaa - 2)
:set sum (7000 + $day + $yyy + ($yyy / 4) - ($yyy / 100) + ($yyy / 400) + ((31 * $mmm) / 12))
:set sum ($sum - (($sum / 7) * 7))
:set result [:pick $daytbl $sum]
:log info "Today is $result"