Re: Converting the time from one timezone to another
- From: "William Stacey [MVP]" <william.stacey@xxxxxxxxx>
- Date: Sat, 18 Feb 2006 18:50:16 -0500
Did you even look at the code I linked for you. It does exactly what you
want. I agree that this sort of thing should be in the BCL, but for now,
you need to roll it yourself. Do you have any issues with the code?
--
William Stacey [MVP]
"Nathan Sokalski" <njsokalski@xxxxxxxxxxx> wrote in message
news:ul4VZsNNGHA.916@xxxxxxxxxxxxxxxxxxxxxxx
| Did you read my posting? I understand the concept of UTC, and the process
of
| getting from servertime to localtime (I even showed the code for this in
my
| posting). My question is "Does .NET have a way of telling me how many
hours
| to subtract, perhaps a function that returns the number of hours to
| add/subtract from UTC that might be something like this:
|
| UtcOffsetForTimezone("EST") would return -5
|
| If I wanted to get the local time for Eastern Standard Time, I could very
| easily just use
|
|
| Date.UtcNow.AddHours(-5)
|
|
| The reason I don't like this method is because since most people know what
| timezone they live in by it's name rather than it's UTC offset, I would
like
| a way to enter the timezone as a parameter in order to find the offset.
| Sure, I could lookup all the timezones and their offsets myself, but I
would
| expect this to already be a part of ASP.NET. This may sound lazy, but if
you
| look at all the other things that are easy but ASP.NET have done for you,
| it's not an unreasonable thing to ask.
| --
| Nathan Sokalski
| njsokalski@xxxxxxxxxxx
| http://www.nathansokalski.com/
|
| "Stephany Young" <noone@localhost> wrote in message
| news:OVjtB6MNGHA.1716@xxxxxxxxxxxxxxxxxxxxxxx
| > Given the other newsgroups you cross-posted to, I have to assume that
you
| > are talking about an ASP.NET application running on a web server halfway
| > around the world, and that your reference to 'local' actually refers to
| > the machine upon which you are viewing the generated 'page' in a web
| > browser.
| >
| > Working on that principle, I also assume that you want to either:
| >
| > 1. Carry out some calculation at the server using a date/time pasesed
| > from the client that represents the a point in time at the client
| > expressed in terms of the time zone where the server is physically
| > situated,
| >
| > or
| >
| > 2. Carry out some calculation at the client using a date/time passed
| > from the server that represents a point of time at the server
| > expressed in terms of the time zone where the client is physically
| > situated.
| >
| > Either way, the most critical aspects of the whole exercise are that:
| >
| > 1. The time zone for both the 'server' and 'client' machines are
| > set correctly,
| >
| > and
| >
| > 2. The date and time for both the 'server' and 'client' machines are
| > regularly corrected using a reliable source.
| >
| > The key to solving the 'problem' is to forget about time zones per se,
and
| > to think in terms of a common point of comparison and the differences
from
| > that point.
| >
| > In terms of date/time we, happily, have the concept of Universal Time
| > Coordinated (UTC) which provides a common reference point for expressing
| > date/time anywhere in the world. For those who haven't caught up yet,
UTC
| > used to be known as Greenwhich Mean Time (GMT).
| >
| > We know that your 'client' machine is physically situated somewhere
within
| > the Eastern Time (US & Canada) time zone which is 5 hours behing UTC. We
| > will take you literally and assume that your 'server' machine is
| > physically located 'halfway around the world', in a time zone that is 5
| > hours ahead of UTC.
| >
| > As long as both machines are configured correctly, they will be aware of
| > daylight saving factors relating to their respective time zones and,
| > therefore daylight saving adjustments will be applied to any date/time
| > calculations automatically.
| >
| > For 'one end' to be able to express date/time factors in terms of the
| > 'other end' then one end has to:
| >
| > 1. Know in advance where the other end is, in relation to UTC,
| >
| > or
| >
| > 2. Be told as required what the date/time is at the other end, in terms
| > of UTC.
| >
| > Knowing in advance where the other end is, in relation to UTC, is not
| > really practical for an ASP.NET application because it would need to
know
| > in advance the location of every machine that could ever submit a
request
| > ot it.
| >
| > So that leaves us with communicating the necessary information as and
when
| > required.
| >
| > The DateTime structure nicely presents us with properties and methods
for
| > dealing with values expressed in terms of UTC.
| >
| > To 'capture' the local date and time as UTC we use:
| >
| > Dim _utc As DateTime = DateTime.UtcNow
| >
| > MySendUTCToOtherEnd(_utc)
| >
| > To convert a UTC date and time to local we use:
| >
| > Dim _remoteutc as DateTime = MyGetUTCFromOtherEnd()
| >
| > Dim _local As DateTime = _remoteutc.ToLocalTime
| >
| > _local now contains a value that represents the date and time from the
| > remote machine expressed in terms of the time zone where the local
machine
| > is physically located.
| >
| > To illustrate with an example:
| >
| > Client machine is UTC - 5 hours
| > Server machine is UTC + 5 hours
| >
| > Client local date/time = February 18, 7:00 PM
| > Server local date/time = February 19, 5:00 AM
| >
| > UTC value passed from client = February 19, 0:00 AM
| >
| > _local as calculated by server = February 19, 5:00 AM
| >
| > and, in reverse:
| >
| > Client machine is UTC - 5 hours
| > Server machine is UTC + 5 hours
| >
| > Server local date/time = February 19, 5:00 AM
| > Client local date/time = February 18, 7:00 PM
| >
| > UTC value passed from server = February 19, 0:00 AM
| >
| > _local as calculated by client = February 18, 7:00 PM
| >
| >
| > "Nathan Sokalski" <njsokalski@xxxxxxxxxxx> wrote in message
| > news:OZBJ1uFNGHA.2300@xxxxxxxxxxxxxxxxxxxxxxx
| >>I asked a question about a week ago about how to get my local time,
since
| >>my application is running on a server halfway around the world. I have
| >>determined that my code would look something like this:
| >>
| >> Dim servertime As Date = Date.Now
| >>
| >> Dim utctime As Date = servertime.ToUniversalTime()
| >>
| >> Dim localtime As Date
| >>
| >>
| >> I know that the last step would be to adjust the utctime value by the
| >> appropriate amount using code such as utctime.AddHours(-5), but I am
| >> looking for a way to get this value by supplying the timezone rather
than
| >> an offset (in other words, I am looking for a function that returns
| >> either a System.TimeSpan or Integer when I enter the timezone) so that
I
| >> can do something such as
| >>
| >> utctime.AddHours(GetTZOffset(TimeZones.EST))
| >>
| >> Is there a function that does this, or any way to get the offset by
| >> submitting the timezone? Thanks.
| >> --
| >> Nathan Sokalski
| >> njsokalski@xxxxxxxxxxx
| >> http://www.nathansokalski.com/
| >>
| >
| >
|
|
.
- References:
- Re: Converting the time from one timezone to another
- From: Stephany Young
- Re: Converting the time from one timezone to another
- From: Nathan Sokalski
- Re: Converting the time from one timezone to another
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