12-hour clock format

test_period.jl

# load Dates module
import Base.Dates: AbstractTime, Month, Millisecond, Year, TimeType, Day, Hour, Minute, Second, Period, periodisless, yearmonthday, days, hour, minute, second, millisecond, default
import Base.Dates: DelimitedSlot, Slot, DayOfWeekSlot, slotparse
import Base.Dates: DateFormat, duplicates

Base.show(io::IO,x::DateTime) = print(io,string(x))

DateTime(dt::AbstractString,df::DateFormat=ISODateTimeFormat) = DateTime(parse(dt,df)...)

function getslot(x,slot::DelimitedSlot,df,cursor)
    endind = first(search(x,df.trans[slot.i],cursor+1))
    if endind == 0 # we didn't find the next delimiter
        s = x[cursor:end]
        return (endof(x)+1, isdigit(s) ? slotparse(slot,s) : default(slot.period))
    end
    return endind+1, slotparse(slot,x[cursor:(endind-1)])
end

function parse(x::AbstractString,df::DateFormat)
    x = strip(replace(x, r"#.*$", ""))
    x = replace(x,df.begtran,"")
    isempty(x) && throw(ArgumentError("Cannot parse empty format string"))
    (typeof(df.slots[1]) <: DelimitedSlot && first(search(x,df.trans[1])) == 0) && throw(ArgumentError("Delimiter mismatch. Couldn't find first delimiter, \"$(df.trans[1])\", in date string"))
    periods = Period[]
    cursor = 1
    for slot in df.slots
        cursor, pe = getslot(x,slot,df,cursor)
        pe != nothing && push!(periods,pe)
        cursor > endof(x) && break
    end
    return sort!(periods,rev=true,lt=periodisless)
end



# base/dates/io.jl

immutable MeridianSlot <: AbstractTime end

slotparse(slot::Slot{MeridianSlot},x) = Hour(lowercase(x) == "pm" ? 12 : 0)

function DateFormat(f::AbstractString,locale::AbstractString="english")
    slots = Slot[]
    trans = []
    begtran = match(r"^.*?(?=[ymuUdHMSsEea])",f).match
    ss = split(f,r"^.*?(?=[ymuUdHMSsEea])")
    s = split(begtran == "" ? ss[1] : ss[2],r"[^ymuUdHMSsEea]+|(?<=([ymuUdHMSsEea])(?!\1))")
    for (i,k) in enumerate(s)
        k == "" && break
        tran = i >= endof(s) ? r"$" : match(Regex("(?<=$(s[i])).*(?=$(s[i+1]))"),f).match
        slot = tran == "" || tran == r"$" ? FixedWidthSlot : DelimitedSlot
        width = length(k)
        typ = 'E' in k ? DayOfWeekSlot : 'e' in k ? DayOfWeekSlot :
              'a' in k ? MeridianSlot :
              'y' in k ? Year : 'm' in k ? Month :
              'u' in k ? Month : 'U' in k ? Month :
              'd' in k ? Day : 'H' in k ? Hour :
              'M' in k ? Minute : 'S' in k ? Second : Millisecond
        option = 'E' in k ? 2 : 'e' in k ? 1 :
                 'U' in k ? 2 : 'u' in k ? 1 : 0
        push!(slots,slot(i,typ,width,option,locale))
        push!(trans,tran)
    end
    duplicates(slots) && throw(ArgumentError("Two separate periods of the same type detected"))
    return DateFormat(slots,begtran,trans)
end



# base/dates/types.jl
function DateTime(periods::Period...)
    y = Year(1); m = Month(1); d = Day(1)
    h = Hour(0); mi = Minute(0); s = Second(0); ms = Millisecond(0)
    for p in periods
        typeof(p) <: Year && (y = p)
        typeof(p) <: Month && (m = p)
        typeof(p) <: Day && (d = p)
        typeof(p) <: Hour && (h += (h + p < Hour(24)) ? p : Hour(0))
        typeof(p) <: Minute && (mi = p)
        typeof(p) <: Second && (s = p)
        typeof(p) <: Millisecond && (ms = p)
    end
    return DateTime(y,m,d,h,mi,s,ms)
end



import Base.Test: @test

f = "u dd, yyyy HH:MM:SS a"
@test string(Dates.DateTime("Apr 1, 2015 1:02:03 AM",DateFormat(f))) == "2015-04-01T01:02:03"
@test string(Dates.DateTime("Apr 1, 2015 1:02:03 PM",DateFormat(f))) == "2015-04-01T13:02:03"
@test string(Dates.DateTime("Apr 1, 2015 13:02:03 AM",DateFormat(f))) == "2015-04-01T13:02:03"
@test string(Dates.DateTime("Apr 1, 2015 13:02:03 PM",DateFormat(f))) == "2015-04-01T13:02:03"
@test string(Dates.DateTime("Apr 1, 2015 12:00:01 AM",DateFormat(f))) == "2015-04-01T12:00:01"
@test string(Dates.DateTime("Apr 1, 2015 12:00:00 AM",DateFormat(f))) == "2015-04-01T12:00:00"
@test string(Dates.DateTime("Apr 1, 2015 12:00:01 PM",DateFormat(f))) == "2015-04-01T12:00:01"
@test string(Dates.DateTime("Apr 1, 2015 12:00:00 PM",DateFormat(f))) == "2015-04-01T12:00:00"

f = "u dd, yyyy a HH:MM:SS"
@test string(Dates.DateTime("Apr 1, 2015 AM 1:02:03",DateFormat(f))) == "2015-04-01T01:02:03"
@test string(Dates.DateTime("Apr 1, 2015 PM 1:02:03",DateFormat(f))) == "2015-04-01T13:02:03"
@test string(Dates.DateTime("Apr 1, 2015 AM 13:02:03",DateFormat(f))) == "2015-04-01T13:02:03"
@test string(Dates.DateTime("Apr 1, 2015 PM 13:02:03",DateFormat(f))) == "2015-04-01T13:02:03"
@test string(Dates.DateTime("Apr 1, 2015 AM 12:00:01",DateFormat(f))) == "2015-04-01T12:00:01"
@test string(Dates.DateTime("Apr 1, 2015 AM 12:00:00",DateFormat(f))) == "2015-04-01T12:00:00"
@test string(Dates.DateTime("Apr 1, 2015 PM 12:00:01",DateFormat(f))) == "2015-04-01T12:00:01"
@test string(Dates.DateTime("Apr 1, 2015 PM 12:00:00",DateFormat(f))) == "2015-04-01T12:00:00"