Hi Tom,
I am writing you a timestamp function now.
(a) is the most refined temporal resolution of your timestamps
milliseconds (1/1_000 seconds)?
(b) do you ever get multiple items that have identical timestamps? (If so,
what is the most you have seen.)
(c) do you want your timestamp to be an integer (best), a float (not a
win), or a string? (If string, all digits or not.)
These timestamps will be derived from UT not from localtime (I do the
converting),
to do otherwise invites various problems down the road. Are all time
values given in your local timezone?
On Wednesday, July 8, 2015 at 10:59:33 AM UTC-4, Tom Breloff 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
>
>
>
