Module: UnixEpoch::ClassMethods

Included in:
DateTime
Defined in:
lib/unix_epoch.rb

Instance Method Summary collapse

Instance Method Details

#from_unix_ts(unix_ts, offset = 0) ⇒ DateTime

Create a new DateTime object from a given Unix Timestamp

Parameters:

  • unix_ts (Fixnum, Bignum) —

    seconds since unix epoch (1970-01-01 00:00:00 UTC)

  • offset (Fixnum, TZInfo::Timezone) (defaults to: 0) —

    offset in seconds from UTC time or an instance of TZInfo::TimeZone

Returns:

  • (DateTime) —

    DateTime object representation of the given Unix TS



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# File 'lib/unix_epoch.rb', line 18

def from_unix_ts(unix_ts, offset = 0)

    if not (offset.respond_to? :to_i or offset.kind_of? TZInfo::Timezone) then
        raise "Invalid value passed for offset: must be an integer or TZInfo::Timezone"
    end

    # step 1) get the delta in days, seconds and nano seconds represented by unix_ts

    delta_days = UnixEpoch._floor(unix_ts / 86_400)
    unix_ts -= delta_days * 86_400

    # unix_ts cannot be negative now, so to_i instead of _floor()
    delta_secs = unix_ts.to_i
    unix_ts -= delta_secs

    delta_nano = unix_ts / 1e9

    # step 2) add these deltas to the jd day and jd sec representation of the unix epoch

    epoch_jd = UnixEpoch.jd_unix_epoch()

    epoch_jd_days = epoch_jd.to_i
    epoch_secs = UnixEpoch.get_jd_secs(epoch_jd) # get left over seconds from our epoch

    jd_days = epoch_jd_days + delta_days

    secs = epoch_secs + delta_secs
    if offset.respond_to? :to_i
        secs += offset # add tz offset back in also
    end
    jd_secs = UnixEpoch.secs_to_jd_secs(secs) + Rational(delta_nano.round, 86_400_000_000)

    if offset.respond_to? :to_i
        return DateTime.from_jd(jd_days, jd_secs, offset)
    elsif offset.kind_of? TZInfo::Timezone
        dt = DateTime.from_jd(jd_days, jd_secs, 0) # first create a new DateTime
        ldt = offset.utc_to_local(dt) # then convert it to our target TZ
        return DateTime.from_jd(ldt.jd, ldt.day_fraction, (ldt.to_i - dt.to_i)) # then create a new DateTime with the current offset
    end
end