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How to convert UTC time to local time ?

F

Hello,

 

In my current project, i mostly use UTC datetimes, except for one process, where we need local time (Paris).

 

For example, i need to convert "2020-04-29 12:00:00" (UTC) to "2020-04-29 14:00:00" (local).

 

To convert my UTC datetimes, I could use the rule "+01:00:00 winter" and "+02:00:00 in summer". However, the day the times changes is never the same from one year to another.

For example, in 2020, Winter time (one hour difference with UTC time) was adopted on October 25th, and Summer time (two hours difference with UTC time) was adopted on March 29th. In 2021, Winter time change will be adopted on October 31st and Summer time will be adopted on March 28th.

 

Moreover, the conversion will not occur at the specified datetime ! This conversion could be run six months later, a year later… because we are processing data long after it was created. So I can not rely on the time of the computer doing the calculs to compute a time difference.

 

I need to avoid any manual intervention, that could lead to a human mistake, on the process, so the conversion must be fully automated.

 

Is there a way to automatically convert my UTC datetimes to Paris datetimes ?

 

I tried looking at the DateTimeConverter transformer, but it seems only formats are manipulated, and not conversion.

 

Best answer by ebygomm

frcoud wrote:

Thanks for your answer ebygomm.

 

The data is not processed on the date it was created. Therefore, i have a datetime to convert that could be from 6 months ago or further… Therefore, I can not rely on the local time of my computer (I edited the question).

The local does not relate to current time, but the time setting of your machine.

 

The formula should return the following if your machine is set to Paris time

e.g. if the attribute date has a value of 20200429120000 (2020-04-29 12:00:00), this formula will return

20200429120000+02:00 (plus 2 as during summertime

 

if the attribute date has a value of 202003428120000 (2020-03-28 12:00:00), it will return

20200328120000+01:00 (plus 1 as before daylight savings started)

 

 

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ebygomm
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  • ebygommInfluencer
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  • October 29, 2020

If your machine is on the local time you want you can use the following

@TimeZoneSet(@Value(date),local,auto)

This will give you the time with offset, which you can then apply

F
  • frcoud
  • Author
  • October 29, 2020

Thanks for your answer ebygomm.

 

The data is not processed on the date it was created. Therefore, i have a datetime to convert that could be from 6 months ago or further… Therefore, I can not rely on the local time of my computer (I edited the question).

ebygomm
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  • October 29, 2020
frcoud wrote:

Thanks for your answer ebygomm.

 

The data is not processed on the date it was created. Therefore, i have a datetime to convert that could be from 6 months ago or further… Therefore, I can not rely on the local time of my computer (I edited the question).

The local does not relate to current time, but the time setting of your machine.

 

The formula should return the following if your machine is set to Paris time

e.g. if the attribute date has a value of 20200429120000 (2020-04-29 12:00:00), this formula will return

20200429120000+02:00 (plus 2 as during summertime

 

if the attribute date has a value of 202003428120000 (2020-03-28 12:00:00), it will return

20200328120000+01:00 (plus 1 as before daylight savings started)

 

 

mark2atsafe
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  • mark2atsafeSafer
  • Safer
  • October 29, 2020

Hi. It's pretty straightforward. This article may be of use: https://community.safe.com/s/article/converting-time-and-date-fields-to-local-timezones

Basically there isn't a transformer, but you use the TimeZoneSet function.

So in an attributeManager you create a new attribute (called zoned for example) with the function:

@TimeZoneSet(@Value(OriginalDateTime),utc)

That creates a new attribute with the UTC timezone attached (if the timezone is already attached, you could leave out that step)

Then a second new attribute (called local for example) with the function:

@TimeZoneSet(@Value(zoned),local)

That creates a new attribute with the local time, such as this:

TimeZoneSetting 

There is one thing to consider: the "local" part of the second function, means use the local timezone of the computer being used. If you were using an Amazon AWS machine - for example - then its local timezone might be different. If you were worried about that, you could replace "local" with your required time zone (eg +01:00).

 

However... if you did hard-code the offset, it might be wrong, because sometimes it will be +1 (standard time) and other times +2 (daylight savings). Using "local" might solve that problem. But I'm going to check with our developers, because I'm not sure if that's true.

 

So I will find out and get back to you. But in the meantime the above functions and the tutorial I pointed to will give you a good starting point.

 

As far as I know, 

ebygomm
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  • October 29, 2020
mark2atsafe wrote:

Hi. It's pretty straightforward. This article may be of use: https://community.safe.com/s/article/converting-time-and-date-fields-to-local-timezones

Basically there isn't a transformer, but you use the TimeZoneSet function.

So in an attributeManager you create a new attribute (called zoned for example) with the function:

@TimeZoneSet(@Value(OriginalDateTime),utc)

That creates a new attribute with the UTC timezone attached (if the timezone is already attached, you could leave out that step)

Then a second new attribute (called local for example) with the function:

@TimeZoneSet(@Value(zoned),local)

That creates a new attribute with the local time, such as this:

TimeZoneSetting 

There is one thing to consider: the "local" part of the second function, means use the local timezone of the computer being used. If you were using an Amazon AWS machine - for example - then its local timezone might be different. If you were worried about that, you could replace "local" with your required time zone (eg +01:00).

 

However... if you did hard-code the offset, it might be wrong, because sometimes it will be +1 (standard time) and other times +2 (daylight savings). Using "local" might solve that problem. But I'm going to check with our developers, because I'm not sure if that's true.

 

So I will find out and get back to you. But in the meantime the above functions and the tutorial I pointed to will give you a good starting point.

 

As far as I know, 

Local will allow for daylight savings, hardcoding it will not

mark2atsafe
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  • mark2atsafeSafer
  • Safer
  • October 29, 2020
ebygomm wrote:

Local will allow for daylight savings, hardcoding it will not

I think you're right. But I asked the dev team to confirm - and to let me know how far back that information goes. Perhaps it's not an issue here, but if I gave it a date in 1978 for example, would it know whether DST applied for not?!

ebygomm
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  • ebygommInfluencer
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  • October 29, 2020
ebygomm wrote:

Local will allow for daylight savings, hardcoding it will not

Yes, i have no idea how it works or how far back it is accurate!

I know i checked the past 5 years by converting every date for the past 5 years and checking that the dates match the daylight savings changes previously

F
  • frcoud
  • Author
  • October 29, 2020
ebygomm wrote:

The local does not relate to current time, but the time setting of your machine.

 

The formula should return the following if your machine is set to Paris time

e.g. if the attribute date has a value of 20200429120000 (2020-04-29 12:00:00), this formula will return

20200429120000+02:00 (plus 2 as during summertime

 

if the attribute date has a value of 202003428120000 (2020-03-28 12:00:00), it will return

20200328120000+01:00 (plus 1 as before daylight savings started)

 

 

​Alright, I managed to make it work !

I first convert my datetime "29-04-2020 12:00:00" to "20200429120000" (with substrings in AttributeManager). Next I apply TimeZoneSet to it. Then I apply TimeZoneGet to its result, to retrieve the "+01" or "+02" and finally I  add this time difference to my time.

Thank you very much, you were a great help !

mark2atsafe
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  • mark2atsafeSafer
  • Safer
  • October 29, 2020
ebygomm wrote:

Local will allow for daylight savings, hardcoding it will not

Also - apologies! I just realized that my answer was the same as yours. Sorry. I wasn't trying to steal your glory. I just wasn't paying enough attention 😵

F
  • frcoud
  • Author
  • October 29, 2020
mark2atsafe wrote:

Hi. It's pretty straightforward. This article may be of use: https://community.safe.com/s/article/converting-time-and-date-fields-to-local-timezones

Basically there isn't a transformer, but you use the TimeZoneSet function.

So in an attributeManager you create a new attribute (called zoned for example) with the function:

@TimeZoneSet(@Value(OriginalDateTime),utc)

That creates a new attribute with the UTC timezone attached (if the timezone is already attached, you could leave out that step)

Then a second new attribute (called local for example) with the function:

@TimeZoneSet(@Value(zoned),local)

That creates a new attribute with the local time, such as this:

TimeZoneSetting 

There is one thing to consider: the "local" part of the second function, means use the local timezone of the computer being used. If you were using an Amazon AWS machine - for example - then its local timezone might be different. If you were worried about that, you could replace "local" with your required time zone (eg +01:00).

 

However... if you did hard-code the offset, it might be wrong, because sometimes it will be +1 (standard time) and other times +2 (daylight savings). Using "local" might solve that problem. But I'm going to check with our developers, because I'm not sure if that's true.

 

So I will find out and get back to you. But in the meantime the above functions and the tutorial I pointed to will give you a good starting point.

 

As far as I know, 

​Yep, that's what I did (I used "local" since I already had the time in UTC).

Thank you for the article !

ebygomm
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  • ebygommInfluencer
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  • October 29, 2020
ebygomm wrote:

The local does not relate to current time, but the time setting of your machine.

 

The formula should return the following if your machine is set to Paris time

e.g. if the attribute date has a value of 20200429120000 (2020-04-29 12:00:00), this formula will return

20200429120000+02:00 (plus 2 as during summertime

 

if the attribute date has a value of 202003428120000 (2020-03-28 12:00:00), it will return 

20200328120000+01:00 (plus 1 as before daylight savings started)

 

 

DateTimeConverter is probably a better way to convert to FME time than with substrings, or @DateTimeParse in the AttributeManager

@DateTimeParse(@Value(date),%d-%m-%Y %H:%M:%S)

 

ebygomm
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  • ebygommInfluencer
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  • October 29, 2020
ebygomm wrote:

Local will allow for daylight savings, hardcoding it will not

Doesn't appear to like the hour between 1 and 2am on the 25th October 2020...

mark2atsafe
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  • mark2atsafeSafer
  • Safer
  • October 29, 2020
ebygomm wrote:

Local will allow for daylight savings, hardcoding it will not

So our developers tell me that we use a big database that is also used by many systems and OSes. I don't know about the 25th October one. We (North America) don't change until next weekend, but I'd be surprised if that caused an issue - unless you were on a virtual machine in this area or using a timezone from over here.

L
  • lija
  • August 9, 2023

Certainly! You can automatically convert UTC datetimes to Paris local time using programming libraries that handle timezone conversions. Most modern programming languages have libraries to manage this task without manual intervention. Here's an example in Python:

from datetime import datetime
import pytz
 
utc_time = datetime.strptime('2020-04-29 12:00:00', '%Y-%m-%d %H:%M:%S')
utc_time = pytz.utc.localize(utc_time)
 
paris_tz = pytz.timezone('Europe/Paris')
local_time = utc_time.astimezone(paris_tz)
 
print(local_time)  # Output: 2020-04-29 14:00:00+02:00

This code snippet automatically handles the Daylight Saving Time changes for Paris, so you don't have to manually apply the "+01:00:00 winter" and "+02:00:00 in summer" rules. The 

pytz

 library, in particular, is aware of these time changes. Similar libraries exist for other languages as well.

 

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