KDM timezones - UI feedback

[carl]

Hi all,

The way KDM validity times are expressed in DCP-o-matic has been quite often discussed, and quite often changed. Here's the story so far...

KDMs have their valid-from and valid-to times expressed as a local time, with a timezone that tells you the offset from the UTC. DCP-o-matic must put these times into KDMs it creates.

The question is: what should the user interface look like when creating KDMs - how do you specify the validity times?

1. In the beginning: cinemas had timezones.

When you added a cinema you would specify the timezone. Then when making KDMs you specified local time, and DCP-o-matic would work out the rest.

Then somebody - I now can't remember who - said that this is no good because cinema timezones change with daylight savings times, and it's not practical to update those timezones. So you run the risk of making a KDM whose validity times are an hour or two out.

2. Phase #2: when making KDMs you specify local time and time zone

My answer to the daylight savings problem was to make it so that when making KDMs you entered the local time with the required time zone. DCP-o-matic would then convert these times to UTC and write them to the KDM with the special timezone "-00:00" (which means "unknown").

Then people said this was no good because daylight savings are not a concern after all (because KDM validity should never be so tightly specified that DST matters...) but timezones are definitely a concern because they can introduce an error of up to 12 hours.

3. Trying to be clever: cinemas have a timezone again

So then I changed it so that cinemas once again have a timezone, and that timezone is pre-filled into the KDM creation dialog box when you make a KDM - but only if all the cinemas you selected to make KDMs for have the same timezone. If they don't we fall back to UTC.

But then this is no good because if you create KDMs for a cinema at UTC+9 and one at UTC+11 at the same time you end up with KDMs in UTC, and the cinema freaks out because they look at times in UTC and think they are all wrong.

[carl]

Now it seems to me that actually the way we had it in step 1 makes the most sense. Does anybody have any thoughts - specifically on whether daylight savings times are a problem if we give each cinema a timezone and always make KDMs for that cinema in its timezone?

[IoannisSyrogiannis]

So you run the risk of making a KDM whose validity times are an hour or two out.

I have worked again and again as a projectionist, or the closest to that.
I find that concern over having a KDM validity window that would be one hour more than necessary to be completely insane and greatly illogical.
...maybe not, when everyone is after you.

What makes sense is to set the date and time of the validity window and have that applied on the time-zone the screen is. Would one care to check a box about daylight saving time and that being taken under account? Superb!
The matter of the fact is that the fine details of the KDM issuing should be discussed with the cinemas and too much optimization will never make perfect. It would save more time, allowing to make many KDMs simultaneously for one screen, or being able to make multiple KDMs for multiple screens at once, than finding a time scheme that would fit everyone's need.

[Carsten]

I always found the original way the best - keeping the time-zone associated with the cinema details, certs, etc.

And I second Ioannis - people should simply not issue KDMs with validity windows that are so short that an hour or two would break playout. That's just nonsense.


Cinemas will hardly ever look into the KDMs themselves - the cinema server will display the KDM validity time adjusted to local time zone and summer-time saving, also the KDM Mail will give that indication based on local time.

[carl]

Great, thanks both. I wish I had recorded who was so sure that daylight savings was a problem so I could talk to them about it! Never mind, I think I will revert to how it used to be in the beginning™.

[IoannisSyrogiannis]

I will go off-topic, because there is no sub-topic of the "General" regarding the forum's function itself.
I am often jealous of the new Film-Tech forum's "Like" function.
On many occasions, I want to "like"(, "+1", etc.) the post of someone without bloating the forum and creating extra posts and pages just to express my having the same view, experience, or simply finding a post enlightening.

This forum's form is well established and one may encounter similarly built forums online. I don't recall seeing one of them with a "like" or "+1" feature. Yet, if there is the choice for such, I would welcome it.