I'm trying to protect game from abusing time changing. The game save current time and if you enter game soon it check if timeInterval is greater than 0 (if not you can't play). But what about changing timeZone?
If player moved from France to e.g. United Kingdom timeZone changes. Let's say first point was 10:07AM in France and the second in UK after 30 minutes (-1 hour difference). The second point is gonna be 09:37AM? How Date() works when devise TimeZone changes? Do timeInterval() function takes into account that changes? Or it possible to just ignore changing timeZone?
Game should working offline.
Update
How that works
The Date() is saved at the very first entry in app. (In CoreData)
The next time the app enters, it will check the new and old dates. Using TimeInterval()
Case1 - result is greater than 0. It means the entry in "Future". Entry allows. Save the new Date instead of the old.
Case2 - result is less than 0. It means the entry in "Past". That impossible without date changing. Entry is prohibited until the new date is greater than old.
From the Date() documentation:
A Date value encapsulate a single point in time, independent of any particular calendrical system or time zone.
I would therefore expect this to be a non-issue - the first point in time would still be 30 minutes before the second point in time, and I'd expect that to be respected by timeInterval. I'd expect the same Date() to be returned by now at a given point in time, regardless of the time zone of the system running the code.
Related
Is there a standard for encoding a date as a timestamp? My thoughts:
This should be 12:00pm UTC in local time, eg 9:00am at T-3, therefore anyone consuming the timestamp, regardless of their -12/+12 offset, will recognize the same date, regardless of whether they parse at the UTC timezone
It could be 12:00pm at UTC
It could be the start of the day (12:00am) at UTC
It could be start of the day (12:00am UTC) in local time eg 9:00pm at T-3
Is there an official spec or standard to adhere to?
It would be easy to point to this document and say 'this is the standard' as opposed to being unaware and having to change our logic down the line.
There isn't a standard for this, because a date and a timestamp are logically two very different concepts.
A date covers the entire range of time on that day, not a specific point in time.
It may be a different date for a person in another time zone at any given point in time, but dates themselves do not have any association with time zones. Visualize a date as just a square on a calendar, not a point on a timeline.
Many APIs will use midnight (00:00) as the default time when a date-only value is assigned to a date+time value. However:
Whether it is UTC based or local-time based is very dependent on that particular API. There is no standard for this, nor is one answer necessarily better than the other.
Assigning a local-time midnight can be problematic for time zones with transitions near midnight. For example, in Santiago, Chile on 2019-09-08, the day started at 01:00 due to the start of DST. There was no 00:00 on that day.
Also, you tagged your question with momentjs. Since a Moment object is basically a timestamp (not a date), then Moment.js will generally assign the start of the day if provided a date-only value. The time zone involved is key to deciding which moment that actually is, which illustrates my prior points.
For example:
// Parsing as UTC
moment.utc('2019-09-08').format() //=> "2019-09-08T00:00:00Z"
// Parsing as Local Time (my local time zone is US Pacific Time)
moment('2019-09-08').format() //=> "2019-09-08T00:00:00-07:00"
// Parsing in a specific time zone (on a day without midnight)
moment.tz('2019-09-08', 'America/Santiago').format() //=> "2019-09-08T01:00:00-03:00"
Also keep in mind that sometimes APIs can be misnamed. The JavaScript Date object is not a date-only value, but actually a timestamp, just like a moment.
I'm creating a customized function that does some calculations for a given time.
When a time is entered in a cell, for example 4:00 PM, this is automatically converted into a date, in this case 12/30/1899 16:00:00 and when the function getTheMinutes() is called, it returns 2 instead of 0.
function getTheMinutes(dateTime){
return dateTime.getMinutes();
}
The behavior of the function is different if it's used for a most recent date like 5/1/2019 16:00:00.
I want the user to be able to just write a time in a cell then use the customized function in another cell. Please let me know your thoughts.
Now that you have indicated the time zone for your spreadsheet I can confirm what #RobG deduced almost a day ago, which is that Guatemala adjusted its difference relative to UTC. Something you have confirmed is treated as by two minutes with effect from October 5, 1918.
More specifically, the adjustment was of 2 minutes and 4 seconds and effective from 03:00 that day:
(Source IANA Version 2019b file northamerica.)
There have been very many such minor adjustments around the world over the years (even between towns in the same country) and adjustments continue, though usually of a whole hour – between 'standard' and Summer time. Sheets has very properly recognised that "normal arithmetic" 'does not work' across such a transition and while noon yesterday to noon today for example is normally, for any one specific location, a difference of 24 hours it is often 23 hours or 25 hours on the day that clocks go forward/back.
And the moral of the story is to beware of obliging Sheets to assume, for want of a specific date, that is has the index number 0 - i.e. is December 30, 1899.
I made some testing, and I found out that the formula is giving a wrong result any minute before 10/5/1918 0:03:00, from that DateTime on, the formula is working as expected.
Here is my sheet https://docs.google.com/spreadsheets/d/1psm8_GJYRczO53TILJCOzo0p4GpnS-ooiGWqOJrC8ZU/edit?usp=sharing
I would need to do a date validation in my customized formula to make it useful. I don't know why google sheets is choosing that date as default when just a time is typed in a cell, I think it should be improved.
val date = "01-10-1967"
val pattern = "dd-MM-yyyy"
val formatter = DateTimeFormat.forPattern(pattern)
formatter.parseMillis(date) // this line fails
The last line fails with:
Cannot parse "01-10-1967": Illegal instant due to time zone offset transition (America/Argentina/Buenos_Aires)
Any idea why?
(JodaTime version is 2.3)
The 1st of October 1967 was in Argentina a day where they changed from standard time to summer time, i.e. added 1 hour, on 00:00.
Since you are not providing a concrete time, I would assume that it defaults to exactly 00:00 which simply did not exist on that day.
Cf. the official faq:
What does 'Illegal instant due to time zone offset transition' mean?
Joda-Time only allows the key classes to store valid date-times. For
example, 31st February is not a valid date so it can't be stored
(except in Partial). The same principle of valid date-times applies to
daylight savings time (DST). In many places DST is used, where the
local clock moves forward by an hour in spring and back by an hour in
autumn/fall. This means that in spring, there is a "gap" where a local
time does not exist. The error "Illegal instant due to time zone
offset transition" refers to this gap. It means that your application
tried to create a date-time inside the gap - a time that did not
exist. Since Joda-Time objects must be valid, this is not allowed.
Possible solutions might be (taken from the faq):
Use LocalDateTime, as all local date-times are valid.
When converting a LocalDate to a DateTime, then use toDateTimeAsStartOfDay() as this handles and manages any gaps.
When parsing, use parseLocalDateTime() if the string being parsed has no time-zone.
Since you aren't interested in time information anyway, I think you might even want to replace formatter.parseMillis(date) with formatter.parseLocalDate(date). If for some reason you still need milliseconds, this Stack Overflow question might help.
How do I get date function to return date according to current system date?
Right now, with the code snippet below, it always returns UK time, not the current system date.
<calculate>
<script>$ = concat( num2date(date(), DateFmt()), " ", num2Time(Time(), TimeFmt()) )</script>
Any help is appreciated!
It's probably not UK time exactly, but rather GMT (or UTC, to use a more precise term). The UK happens to be aligned to GMT in the winter, but in the summer it advances one hour to BST for daylight saving time.
Now, I've never used LiveCycle myself, but nonetheless, I've read through the somewhat minimal docs for LiveCycle FormCalc Date and Time Functions, and the spec, and it appears to me that a few critical mistakes were made.
The date and time functions return UTC-based values, but only the time-related functions have been made aware of the local time zone. That is, there are separate Num2Time and Num2GMTime functions, but there is only one Num2Date function.
The Num2Date function works in terms of whole integer days, and thus they are simply days since 1900-01-01. Therefore, the number being passed in to the function must already be representative of the desired time zone. However, the Date function only gets the current GMT date. There does not appear to be a function to get the current local date.
It's different on the time side, because of the millisecond precision involved. However, there's yet another flaw here. Despite the docs saying that the Time function returning "the number of milliseconds since the epoch", its actually returning only the number of milliseconds since midnight GMT. There is no day-over-day accumulation of milliseconds from the date part. The docs here are even lying in their sample code which says:
Returns the current system time as the number of milliseconds since the epoch.
Time() => 71533235 at precisely 3:52:15 P.M. on September 15th, 2003 to a user in the Eastern Standard Time (EST) zone.
If that was indeed the case (and ensuring to use their 1900-01-01 epoch), the value would actually include an additional 3272572800000 milliseconds representing the days between 1900-01-01 and 2003-09-15, bringing the total timestamp to 3272644333235. Additionally, there's a typo there, because the timestamp they give is 3:52:13, not 3:52:15. Clearly nobody paid close attention to these docs!
The real problem is that one cannot be certain that the number of milliseconds since midnight of the current day in the local time zone is the same on every day. If instead of getting the current time, you were working with past stored time values, you might be an hour off (+ or -) if the current offset is different due to daylight saving time. Example: Eastern time might be UTC-5 or UTC-4, but only the offset currently in effect will be used by the Num2Time function, even if the date you're working with is using the other offset.
So, in summary, the Date function is insufficient, leading to your observations, and the date/time functionality in general is poorly designed. Given the constraints of this API, I can't even recommend a workaround. There would have to be a LocalDate function of some kind to be used instead of the Date function, but it doesn't exist.
The only advice I can offer is that it appears (from my research, not experience) that LiveCycle can use either FormCalc or JavaScript. So - use JavaScript instead.
What time of day are the periods? For example, if I have 2013-06-02 for "start-date", does that start at the beginning of the day at 00:00? If I have 2014-01-03 for "end-date", does that mean it ends at the end of the day at 23:59?
If this is true, setting "start-date" and "end-date to the same value will mean it will only return data that has happened during that day?
To put in less words, are both the start and end dates inclusive or exclusive?
That's correct. the dates are inclusive. If you set both start-date and end-date to the same value you will get all data for that specific day.
Also worth noting that they respect the time zone you configured in your View Settings.