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Fixed daylight saving time

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* When formatting timezone, substract 1 hour from timezone when isDST
 * Do not depend DST in current timezone when parsing arbitrary date
   because formatted timestamps are never in DST.
 * On the way, removed an unnecessary line in parsing code which could
   cause bugs.
 * Added DST tests
This commit is contained in:
Felix Krause 2016-11-10 22:22:48 +01:00
commit 544a2cfe1a
2 changed files with 38 additions and 20 deletions
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35
lib/pure/times.nim
View file

@ -144,8 +144,9 @@ type
yearday*: range[0..365] ## The number of days since January 1, yearday*: range[0..365] ## The number of days since January 1,
## in the range 0 to 365. ## in the range 0 to 365.
## Always 0 if the target is JS. ## Always 0 if the target is JS.
isDST*: bool ## Determines whether DST is in effect. Always isDST*: bool ## Determines whether DST is in effect.
## ``False`` if time is UTC. ## Semantically, this adds another negative hour
## offset to the time in addition to the timezone.
timezone*: int ## The offset of the (non-DST) timezone in seconds timezone*: int ## The offset of the (non-DST) timezone in seconds
## west of UTC. Note that the sign of this number ## west of UTC. Note that the sign of this number
## is the opposite of the one in a formatted ## is the opposite of the one in a formatted
@ -824,28 +825,32 @@ proc formatToken(info: TimeInfo, token: string, buf: var string) =
if fyear.len != 5: fyear = repeat('0', 5-fyear.len()) & fyear if fyear.len != 5: fyear = repeat('0', 5-fyear.len()) & fyear
buf.add(fyear) buf.add(fyear)
of "z": of "z":
let hours = abs(info.timezone) div secondsInHour let
if info.timezone <= 0: buf.add('+') nonDstTz = info.timezone - int(info.isDst) * secondsInHour
hours = abs(nonDstTz) div secondsInHour
if nonDstTz <= 0: buf.add('+')
else: buf.add('-') else: buf.add('-')
buf.add($hours) buf.add($hours)
of "zz": of "zz":
let hours = abs(info.timezone) div secondsInHour let
if info.timezone <= 0: buf.add('+') nonDstTz = info.timezone - int(info.isDst) * secondsInHour
hours = abs(nonDstTz) div secondsInHour
if nonDstTz <= 0: buf.add('+')
else: buf.add('-') else: buf.add('-')
if hours < 10: buf.add('0') if hours < 10: buf.add('0')
buf.add($hours) buf.add($hours)
of "zzz": of "zzz":
let let
hours = abs(info.timezone) div secondsInHour nonDstTz = info.timezone - int(info.isDst) * secondsInHour
minutes = (abs(info.timezone) div secondsInMin) mod minutesInHour hours = abs(nonDstTz) div secondsInHour
if info.timezone <= 0: buf.add('+') minutes = (abs(nonDstTz) div secondsInMin) mod minutesInHour
if nonDstTz <= 0: buf.add('+')
else: buf.add('-') else: buf.add('-')
if hours < 10: buf.add('0') if hours < 10: buf.add('0')
buf.add($hours) buf.add($hours)
buf.add(':') buf.add(':')
if minutes < 10: buf.add('0') if minutes < 10: buf.add('0')
buf.add($minutes) buf.add($minutes)
of "": of "":
discard discard
else: else:
@ -1000,7 +1005,6 @@ proc parseToken(info: var TimeInfo; token, value: string; j: var int) =
of "M": of "M":
var pd = parseInt(value[j..j+1], sv) var pd = parseInt(value[j..j+1], sv)
info.month = Month(sv-1) info.month = Month(sv-1)
info.monthday = sv
j += pd j += pd
of "MM": of "MM":
var month = value[j..j+1].parseInt() var month = value[j..j+1].parseInt()
@ -1166,6 +1170,7 @@ proc parse*(value, layout: string): TimeInfo =
info.hour = 0 info.hour = 0
info.minute = 0 info.minute = 0
info.second = 0 info.second = 0
info.isDST = false # DST is never encoded in timestamps.
while true: while true:
case layout[i] case layout[i]
of ' ', '-', '/', ':', '\'', '\0', '(', ')', '[', ']', ',': of ' ', '-', '/', ':', '\'', '\0', '(', ')', '[', ']', ',':
@ -1195,14 +1200,6 @@ proc parse*(value, layout: string): TimeInfo =
parseToken(info, token, value, j) parseToken(info, token, value, j)
token = "" token = ""
# We are going to process the date to find out if we are in DST, because the
# default based on the current time may be wrong. Calling getLocalTime will
# set this correctly, but the actual time may be offset from when we called
# toTime with a possibly incorrect DST setting, so we are only going to take
# the isDST from this result.
let correctDST = getLocalTime(toTime(info))
info.isDST = correctDST.isDST
# Now we process it again with the correct isDST to correct things like # Now we process it again with the correct isDST to correct things like
# weekday and yearday. # weekday and yearday.
return getLocalTime(toTime(info)) return getLocalTime(toTime(info))

23
tests/stdlib/ttime.nim
View file

@ -201,4 +201,25 @@ for tz in [
let ti = TimeInfo(monthday: 1, timezone: tz[0]) let ti = TimeInfo(monthday: 1, timezone: tz[0])
doAssert ti.format("z") == tz[1] doAssert ti.format("z") == tz[1]
doAssert ti.format("zz") == tz[2] doAssert ti.format("zz") == tz[2]
doAssert ti.format("zzz") == tz[3] doAssert ti.format("zzz") == tz[3]
block dstTest:
let nonDst = TimeInfo(year: 2015, month: mJan, monthday: 01, yearday: 0,
weekday: dThu, hour: 00, minute: 00, second: 00, isDST: false, timezone: 0)
var dst = nonDst
dst.isDst = true
# note that both isDST == true and isDST == false are valid here because
# DST is in effect on January 1st in some southern parts of Australia.
doAssert nonDst.toTime() - dst.toTime() == 3600
doAssert nonDst.format("z") == "+0"
doAssert dst.format("z") == "+1"
# parsing will set isDST in relation to the local time. We take a date in
# January and one in July to maximize the probability to hit one date with DST
# and one without on the local machine. However, this is not guaranteed.
let
parsedJul = parse("2016-07-01 04:00:00+01:00", "yyyy-MM-dd HH:mm:sszzz")
parsedJan = parse("2016-01-05 04:00:00+01:00", "yyyy-MM-ss HH:mm:sszzz")
doAssert toTime(parsedJan) == fromSeconds(1452394800)
doAssert toTime(parsedJul) == fromSeconds(1467342000)