[SITE] display time in local user time zone

[toshywoshy]

Fixes #9819

• add local user time zone
• add offset from UTC to convert
• convert event time to user time zone
• add several examples to demo

This solves issue #9819 and provides a way to display user local time for the program for start_time and end_time.
It uses the users browser defined time zone, and provide the timezone name and the time based.
An event needs to add timeoffset: "+0200" to indicate the offset of the timezone against UTC.
Please note that this value needs to be quoted as a string.
Here are some examples, which have also added into this commit

• London : +0100
• Rio de Janero : -0300
• Denver : -0600

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[mattstratton]

An event needs to add timeoffset: "+0200" to indicate the offset of the timezone against UTC.

What happens with events that do not have the offset?

[toshywoshy]

• So if you do not set a timezone or an offset, the old normal progam is displayed.
  Check any event in this preview, for example : https://deploy-preview-14405--devopsdays-web.netlify.app/events/2024-organiser-summit/program

• If you do set timezone and no offset, it will caclulate the offset and set show the timezone after the hours
  The example here is "London" : https://deploy-preview-14405--devopsdays-web.netlify.app/events/2024-london/program

• If you do not set timezone and only the offset, if will just display the local time with no other indication
  The example here is "Denver" : https://deploy-preview-14405--devopsdays-web.netlify.app/events/2024-denver/program

• If you do set both timezone and offset, it will combine all features
  The example here is "Rio de Janero" : https://deploy-preview-14405--devopsdays-web.netlify.app/events/2024-rio-de-janeiro/program

Program

Program for devopsdays organiser-summit 2024

Devopsdays London 2024 Program

If Open Space is new to you, you may be interested in more details about Open Space. Schedule is subject to change and more details will be added periodically Color Keys: Talk Ignite Open Space

Program

Program for devopsdays Denver 2024

Program

Program for for devopsdays Rio 2024

[phrawzty]

What happens if there's a summer/winter time shift during an event?

[toshywoshy]

If you use timezone it will display the summer/winter time correctly, as the offset gets calculated
If you use offset, then it will be in summer of winter time based upon the entry and the change will not be automatic

[mattstratton]

This seems good! There's a merge conflict that needs resolution @toshywoshy and then I'll merge it

We do need to update the REFERENCE.md with the new fields too.

[mattstratton]

There's a merge conflict that needs resolution

I think i fixed that :)