m0=: 6!:0

System time stamp yyyy mm dd hh mm ss (argument y needed but ignored)

m1=: [:<._3:{.]

hh mm ss part of time stamp

m2=: 1000"_ #. ]

Base-1000 form of y

m3=: (':'"_) _6 _3} ":

Format with ':' between fields

m4=: [:<.3:{.]

yyyy mm dd part of time stamp

m5=: ('/'"_) 4 7} ":

Format with '/' between fields

m6=: [: m3 [: m2 [: m1 m0

Formatted time stamp hh:mm:ss

m7=: [: m5 [: m2 [: m4 m0

Formatted date stamp yyyy/mm/dd

m8=: (':'"_) 2 5} [: ": 1000"_ #. _3: {. [: <. m0

Formatted time stamp hh:mm:ss

m9=: ('/'"_) 4 7} [: ": 1000"_ #.  3: {. [: <. m0

Formatted date stamp yyyy.mm/dd

m10=: 100"_#.100"_|3:{. m0

yymmdd from ccyy mm dd (y neglected)

m11=: 0: ~:/ .= 4 100 400"_ |/ ]

Is y a leap year?

m12=: 28"_ + m11@]

Number of days in February of year y

d13=: 31"_ - 2: | 7: | [

31 - 2 | 7 | x: days in month x, not = 1

d14=: d13`m12@.([=1:)

Number of days in month x of year y

m15=: ('0123456789 '"_ i.[:":[:|. 3: {. 6!:0) { ('0123456789.'"_)

Current date in dd.mm.yy fmt, neglect y

m16=: ((12"_ <: {.),2:) { 'apm'"_

am or pm depending on first atom of y

m17=: ([: m3 m2) , (' '"_ , m16)

Formatted 3-atom time y in 'm' form

m18=: [:":[:(1:|.])100"_|[:m4 m0

Formatted date in mm dd yy form

m19=: '/'"_(]#[:i.#)@(' '"_=])}]

Replace blanks in y by '/'

m20=: m19@m18

Formatted date in mm/dd/yy form

m21=: >:@(365&* + m22)@(-&1601)

# of New Year’s Day, Gregorian year y; m21 1601 is 1

m22=: -/@:<.@(%&4 100 400)"0

# of leap days in y years (Clavian corr.)

m23=: 7&|@m21

Day of week year y begins (0=Sunday)