MikroTik

#use the system clock date or one of our choosing
#:local date [/system clock get date]
:local date jan/12/2019

#Variables
:local result ""
:local daytbl [:toarray "sun,mon,tue,wed,thu,fri,sat"]
:local MonthNum 0
:local CenturyNum 0
:local YearNum 0
:local SUM 0


#Parse the input date
:local month [:pick $date 0 3]
:local day [:pick $date 4 6]
:local year [:pick $date 7 11]

#perform the month offset per the algorithm
:if ($month = "jan") do={ :set MonthNum 11}
:if ($month = "feb") do={ :set MonthNum 12}
:if ($month = "mar") do={ :set MonthNum 1}
:if ($month = "apr") do={ :set MonthNum 2}
:if ($month = "may") do={ :set MonthNum 3}
:if ($month = "jun") do={ :set MonthNum 4}
:if ($month = "jul") do={ :set MonthNum 5}
:if ($month = "aug") do={ :set MonthNum 6}
:if ($month = "sep") do={ :set MonthNum 7}
:if ($month = "oct") do={ :set MonthNum 8}
:if ($month = "nov") do={ :set MonthNum 9}
:if ($month = "dec") do={ :set MonthNum 10}

#perform the year offset based on month per the algorithm
:if ($MonthNum = 11) do={ :set year ($year-1)}
:if ($MonthNum = 12) do={ :set year ($year-1)}

#start the date math
:set CenturyNum ($year/100)
:set YearNum ($year % 100)

#gets a little weird here without decimals...
:local decimalOne "2.6"
:local decimalTwo ".2"

#do some decimal math
:set SUM ($decimalOne * $MonthNum - $decimalTwo)

#looks like numbers get converted to date data type, strip off what we need
:set SUM [:pick $SUM 6 8]

:set SUM ($SUM + $day + $YearNum)

:set SUM ($SUM + $YearNum/4)

:set SUM ($SUM + $CenturyNum/4)

:set SUM ($SUM - 2 * $CenturyNum)

:set SUM ($SUM % 7)

:if ($SUM < 0) do= {:set SUM ($SUM+7)}

:set result [:pick $daytbl $SUM]
:put $result

#
#	$RCSfile: function-date.rsc,v $
#	$Revision: 1.1 $
#	$Date: 2011/05/27 19:47:46 $
#	$Author: reesejb $, iNet Specialists. Copyright, (C)2007-2011, All Rights Reserved
#
#	Calculates day of the week (number of month, etc.) for a givien date
#
#	Expanded from "day of week" script at:
#		http://wiki.mikrotik.com/wiki/Script_to_find_the_day_of_the_week
#	
#	Month: jan,feb,..nov,dec   (must be lower-case)
#	Day: 01-31
#	Year: 1900-2999
#	mmm/dd/yyyy   same format as [/system clock get date]
#	(ex. jul/22/2009)

:local date [/ system clock get date]

# Variables
:global weekday ""
:global monthord ""
:local months [:toarray "jan,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec"]
:local monthval [:toarray "01,02,03,04,05,06,07,08,09,10,11,12"]
:local monthtbl [:toarray "0,3,3,6,1,4,6,2,5,0,3,5"]
:local daytbl [:toarray "sun,mon,tue,wed,thu,fri,sat"]

:global monthshort [:pick $date 0 3]
:global day [:pick $date 4 6]
:local daysum $day
:local dayc [:pick $date 5 6]
:global century [:pick $date 7 9]
:global year [:pick $date 9 11]
:local yearsum $year
:local yearc [:pick $date 10 11]

# if the first digit of the day or year is a 0 (zero),
# only use the last digit, otherwise the script will fail
:if ([:pick $date 4 5] = 0) do={ :set daysum ($dayc)}
:if ([:pick $date 9 10] = 0) do=[:set yearsum ($yearc)]

# Calculate "sum" to determine which "day of week" (from daytbl) to use
:local sum 0
:set sum ($sum + (2 * (3 - ($century - (($century / 4) * 4)))))
:set sum ($sum + ($yearsum / 4))
:set sum ($sum + $yearsum + $daysum)
:for mindex from=0 to=[:len $months] do={ \
	:if ([:pick $months $mindex] = $monthshort) do={ \
		:set sum ($sum + [:pick $monthtbl $mindex])
		:set monthord [:pick $monthval $mindex]
		} \
	}
:set sum ($sum - (($sum / 7) * 7))
:set weekday [:pick $daytbl $sum]

# Log the result for troubleshooting purposes
:log info "Today is $weekday, $monthshort $day, $century$year ($monthord/$day/$century$year)"

# 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"