CODEWITHSUNDEEP
javamysqldatetimedatetime-formatdate-comparison
Linda
Linda

Reputation: 11

Does the time change affect Java date compare function?

We are trying to compare a date stored in mySQL with a plain text date field read from the original of a Gmail message, using java date compare.

First time through, the Gmail message plain text Date is read and stored in a mySQL database field “date_sent” type TIMESTAMP. The next time that message is checked, it gets the message plain text Date and, using the Java date compare function, compares that with the stored date_sent value.

This compare usually works. However -- if the date and time of the message Date being compared is during the 1am hour on a day in which the time changed (daylight savings to standard), the compare fails.

Has anyone experienced this? how were you able to fix it?

Upvotes: 1

Views: 191

Answers (2)

Dawood ibn Kareem
Dawood ibn Kareem

Reputation: 79875

It seems like you've got an uphill battle. If a message arrives, dated 1:30am, on the date when Daylight Savings ends, I don't think there's any way you can tell whether it's the FIRST occurrence of 1:30am (before the clocks go back) or the SECOND.

Presumably, you'll never get a message dated 1:30am on the date when Daylight Savings starts, because this time won't actually exist.

So if you do this by converting the text field to a date and storing it, you'll always have an issue of how to compare such dates. Your comparison might be wrong sometimes if you pick the wrong 1:30am, and I don't think there's too much you can do about it, if you want your timezones to be correct, for both Daylight Savings Time and Standard Time.

One thing you might consider doing is storing the timestamps as text, not as dates, so that the conversion never happens. If you use a format like yyyy-MM-dd HH:mm:ss then you should be able to do a text comparison instead of a date comparison, and get the correct results.

Upvotes: 2

Daniel Kaplan
Daniel Kaplan

Reputation: 67514

I've never experienced this because I've never done it. What I think you'll have to do is get/know the timezone of the text date, convert it into a Date object (using that timezone), then compare the dates that way.

You say you're using the Date compare method, but that says it requires a Date as input. So are you already converting? Please show us that code. Are you passing in a timezone?

Also, this question has very useful information that you can use.

Upvotes: 1

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