TimeZones.jl isn't quite ready for public consumption yet (enough public
clamor will eventually get me to fix it up).
How about the following?
function calcSecondsEpochToMidnight(secondsSinceEpoch::Integer)
utc = DateTime(Date(Dates.unix2datetime(secondsSinceEpoch)))
adjustment = Dates.Second(div(Dates.value(now() - now(Dates.UTC)),1000))
return Dates.value(utc+adjustment)
end
Obviously this will only work if you're in EST (now() will return a
DateTime according to your system time), so it's not very portable, but it
also doesn't require any other timezone fiddling.
-Jacob
On Wed, Jul 8, 2015 at 8:59 AM, Tom Breloff <t...@breloff.com> wrote:
> I have some code which requires figuring out the number of seconds from
> the Epoch until midnight (local time) in order to quickly compute the local
> TimeOfDay. The reason is that I get passed a field which is seconds since
> Epoch, and I'd like to just subtract off the (cached) # seconds from
> Epoch-->Midnight.
>
> Since I'm using a cached number, I don't care so much how long it takes to
> calculate. Right now I use both Dates and Calendar.jl, but I'm wondering
> if I can accomplish this without the dependency on Calendar.jl (which I
> currently use ONLY to get the hours offset between Eastern US and UTC). Is
> there a better way to write this function?
>
>
> function getHoursAdjustmentFromUTC(year::Integer, month::Integer,
> day::Integer)
> millisEST = *Calendar.ymd*(year, month, day, "EST5EDT").millis
> millisUTC = *Calendar.ymd*(year, month, day, "UTC").millis
> UInt64(round((millisEST - millisUTC) / (secondsInOneHour *
> millisInOneSecond)))
> end
>
> getEpochMillis() = UInt64(DateTime(1970,1,1).instant.periods.value)
> createUTCDateTimeFromSecondsSinceEpoch(secondsSinceEpoch::Integer) =
> DateTime(Dates.UTM(secondsSinceEpoch * millisInOneSecond +
> getEpochMillis()))
>
>
> # this is the function I care about... note that "midnight" refers to
> midnight local to Eastern US
> function calcSecondsEpochToMidnight(secondsSinceEpoch::Integer)
>
> dt = createUTCDateTimeFromSecondsSinceEpoch(secondsSinceEpoch)
>
> # get the hour adjustment using the Calendar module
> y = Dates.year(dt)
> m = Dates.month(dt)
> d = Dates.day(dt)
> hourAdjustment = getHoursAdjustmentFromUTC(y, m, d)
>
> millisMidnightUTC::UInt64 = DateTime(y, m, d).instant.periods.value
> millisMidnightEST::UInt64 = millisMidnightUTC + hourAdjustment *
> secondsInOneHour * millisInOneSecond
>
> return UInt64((millisMidnightEST - getEpochMillis()) / millisInOneSecond)
> end
>
>
>
