Working With Dates

Working with Dates (and Timezones)

First of all the constructor:

new Date()

…will make the same date no matter what timezone you are in.

So if you do new Date() in The Netherlands and at the same time somebody else does new Date() in USA, then that is the exact same date. Both represent the time in milliseconds after 1970 in UTC. This is called Unix Time.

The only thing that makes it look different is when you print or format it. The toString() of a date already formats it, so it shows the date and timezone you are currently in. But this does not mean that Dates have a timezone — that is not correct.

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Constructors

new Date(year, month[, day[, hour[, minutes[, seconds[, milliseconds]]]]]);

Those arguments are then in your timezone. Just like formatting a string with "yyyy/MM/dd HH:mm" using your timezone in the formatter.

There is also:

Date.UTC(year, month, date, hrs, min, sec, ms)

This function returns the milliseconds in UTC (you can wrap this in new Date(number)). So if you pass hrs = 10 and you are in +2, then the date in your timezone will be 12.

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Local vs Server Time in Servoy

In Servoy the problem arises when you call methods like Date#getHours() because they use local time.

• The server could be in timezone +2

• The client could be in timezone +3

• Servoy code runs on the server, so getHours() will reflect the server's timezone (same as toString()).

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Example: Local or UTC Time with getHours()

var date1 = new Date(2019,10,1,12);
var date2 = new Date(Date.UTC(2019,10,1,12));

application.output(date1);
application.output(date2);
application.output(date1.getHours());
application.output(date2.getHours());

Output:

• date1 prints 12 in both cases (constructed for local time).

• If you are in +1, then date2 prints 13 because UTC 12 is 13 in Amsterdam.

⚠️ But this is always based on the server timezone, not the client (which may be different again).

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Getting the Client's Hours (NGClient and SmartClient)

You can use:

application.output(utils.dateFormat(date1, "HH"));

This uses the client's timezone (from the browser).

Example:

• Server in +1

• NGClient in +2

• The code prints 13, since 12:00 in the server's timezone is 13:00 in the client's.

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Use as LocalDateTime

In NGClient, the Use as LocalDateTime option (date format dialog) controls how dates are sent.

• Default (unchecked): Sent as ISO-8601 with timezone, e.g. 2019-11-01T12:00:00+01:00 (server in +1). Client in +2 shows it as 2019-11-01 13:00. (Milliseconds don't change — purely formatting.)

• Checked (Use as LocalDateTime): Sent without timezone, e.g. 2019-11-01T12:00:00 Client assumes it's in its timezone and shows 2019-11-01 12:00.

⚠️ Problem: now the milliseconds do change, since the date was shifted by the difference between server and client timezone.

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application.getTimeStamp()

If you are using Use as LocalDateTime, you may need a date that represents "now" on the client.

• new Date() on the server (timezone +1) could give 2019-11-28 23:00.

• application.getTimeStamp() in the client (timezone +2) would give 2019-11-29 00:00.

This ensures the date matches the client's actual local "now."

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Searching Between Dates

When searching (e.g. "everything from yesterday"), you need dates relative to the client's timezone.

Example in +2:

var startDate = utils.parseDate("2019-11-28 00:00", "yyyy-MM-dd HH:mm", null);
var endDate   = utils.parseDate("2019-11-28 23:59", "yyyy-MM-dd HH:mm", null);

• The null argument (new in Servoy 2019.12) tells it to use the client's timezone.

• If you omit it, the server timezone is used.

Server in +1, client in +2 would produce:

Wed Nov 27 23:00:00 CET 2019
Thu Nov 28 22:59:00 CET 2019

If sent back to the client (with Use as LocalDateTime = false), the browser adds back the difference (1 hour), so the date correctly represents the client's "yesterday."