B4J Question Inconsistency in DateTime

[aminoacid]

I wonder why, when the following code is run on a Windows PC it returns the LOCAL time and when the same code is run on a LINUX machine, it returns UTC time. Is there any way to resolve this inconsistency? I understand that DateTime.Now is supposed to return the UTC time but on a PC it returns the Local time.

    ' Calculate Time Stamps
    hrmin=(DateTime.GetHour(DateTime.Now)) * 100 + DateTime.GetMinute(DateTime.Now)
    moday=(DateTime.GetMonth(DateTime.Now)) * 100 + DateTime.GetDayOfMonth(DateTime.Now)

 

[OliverA]

Are you sure DateTime.Now is not returning UTC time? Why don't you just log DateTime.Now, and use https://currentmillis.com/ to determine if it is UTC or not. On my Windows 10 system, I get UTC. Please note that GetHour, GetMonth should return your local time information (those methods take into account your time zone settings).

 

[OliverA]

If you want to use UTC with the GetHour/GetMonth methods, you'll have to save the current timezone offset, set the timezone offset to 0 (zero), use the methods and then restore your timezone offset.

    Dim aTime As Long = DateTime.Now
    Log(aTime)
    Dim offset As Double = DateTime.GetTimeZoneOffsetAt(aTime)
    Log($"GetHour with current timezone offset of ${offset}: ${DateTime.GetHour(aTime)}"$)
    DateTime.SetTimeZone(0)
    Log($"GetHour with no timezone offset: ${DateTime.GetHour(aTime)}"$)
    DateTime.SetTimeZone(offset)
    Log($"GetHour after restoring timezone offset to ${offset}: ${DateTime.GetHour(aTime)}"$)

 

[aminoacid]

Thanks OliverA! I should have said the code (not DateTime.Now) is returning Local time on a Windows PC and UTC time on a Linux Machine.
OK, so I understand that the GetHour/GetMonth methods will return Local Time. But then why the inconsistency on a Linux machine where they return UTC time instead? That's what's confusing to me.

 

[OliverA]

Have you tried running the code on the Linux box? Could be that the system timezone is set to UTC (if the current timezone offset logs to 0 (zero)), which at that point is then a configuration issue on the Linux box, not a JVM/Java/B4J issue.

 

[aminoacid]

Yes, I developed the program on a Windows 10 PC and noticed that the date/time was showing local as expected when the JAR file was run. Then taking the same JAR file unmodified to a Linux box running Ubuntu, I noticed that the date/time was UTC. So the first thing I checked was the system timezone settings on the Linux box and it was set to UTC. I changed it to the local time zone, but still get this inconsistency.

 

[aminoacid]

Ignore the last message .... I guess that after you change the time zone on a Linux box you need to reboot even though the new time shows up immediately. I rebooted and now the applications displays the local time as it should.

Thanks for your help OliverA, your sample code above should however be very useful for future reference.

 

[Erel]

This code looks very wrong:

  hrmin=(DateTime.GetHour(DateTime.Now)) * 100 + DateTime.GetMinute(DateTime.Now)
    moday=(DateTime.GetMonth(DateTime.Now)) * 100 + DateTime.GetDayOfMonth(DateTime.Now)

Watch the date and time video tutorial: https://www.b4x.com/etp.html?vimeography_gallery=1&vimeography_video=256970493

 

[aminoacid]

This code looks very wrong:

  hrmin=(DateTime.GetHour(DateTime.Now)) * 100 + DateTime.GetMinute(DateTime.Now)
    moday=(DateTime.GetMonth(DateTime.Now)) * 100 + DateTime.GetDayOfMonth(DateTime.Now)

Watch the date and time video tutorial: https://www.b4x.com/etp.html?vimeography_gallery=1&vimeography_video=256970493

Erel, I looked at the video and could not find anything wrong. The code works fine. The problem was with the Linux box not applying the timezone setting change immediately. What I am doing here is getting the current hours, minutes, month and day, formatted as two 16-bit integers. The way it's formatted may look strange but this is the requirement for the application. And it does what it was intended to do. Do you see a potential issue? Thanks!

 

[Erel]

Do you see a potential issue?

No. Now I understand what you are doing

 

[aminoacid]

Vhew! OK Thanks! Appreciate you looking over my shoulder It always helps.