Apex DateTime formatting for Dynamic SOQL query returning wrong value

Question

I am passing a DateTime as a Long into my Apex controller and storing it in a variable called start, and it has a value of:

1528329130300

When I create a DateTime from the Long

DateTime startDateTime = DateTime.newInstance(start);
System.debug('startDateTime: ' + startDateTime);

I get the expected output:

startDateTime: 2018-06-06 23:52:10

But when I format it for use in a Dymanic SOQL query like this:

startDateTime.format('yyyy-MM-dd\'T\'hh:mm:ss\'Z\'')

I get a different day and time:

2018-06-07T12:52:10Z

I am using this DateTime to query and the difference in value is leaving out records I am expecting to get.

What am I doing wrong with the DateTime formatting?

Answer 1

You can format the Datetime instance according to GMT:

String correctTimeZoneValue = DateTime.newInstance(myLong).formatGMT(myFormat);

Answer 2

To get the correct value formatted as a String for the Dynamic SOQL Query, I needed to use this:

startDateTime.formatGMT('yyyy-MM-dd\'T\'HH:mm:ss\'Z\'')

Note:

1) the use of DateTime.formatGMT(format); as Adrian Larson suggested

and

2) the hour needed to be HH rather than hh

---

Apex code used to debug:

TimeZone tz = UserInfo.getTimeZone();
System.debug('String format: ' + tz.toString());
System.debug('Display name: ' + tz.getDisplayName());
Long start = Long.valueOf('1528329130300');
System.debug('start: ' + start);
DateTime startDateTime = DateTime.newInstance(start);
System.debug('startDateTime: ' + startDateTime);
System.debug('Offset: ' + tz.getOffset(startDateTime));
System.debug('startDateTime: ' + startDateTime.formatGMT('yyyy-MM-dd\'T\'HH:mm:ss\'Z\''));