OK so for example, today is Tuesday, Feb 02. Well the equivalent "Tuesday" from last year was on Feb 03.
How can I find this out programmatically?
Thanks!!
+2
A:
According to Google, there are 604,800,000 milliseconds in a week. That times 52 should give you the same day of the week a year later (right?).
For example:
var date:Date = new Date(2010, 1, 2);
trace(date);
date.setMilliseconds(date.milliseconds - 604800000 * 52);
trace(date);
Output:
Tue Feb 2 00:00:00 GMT-0800 2010
Tue Feb 3 00:00:00 GMT-0800 2009
Stiggler
2010-02-02 18:52:05
I think you may have meant to say 604 800 000ms in a *week* not a year.
Dan
2010-02-02 18:58:41
Yikes, it was a simple typo people; I obviously meant week.
Stiggler
2010-02-02 19:02:30
definitely not enough of a typo for a downvote.
invertedSpear
2010-02-02 19:05:20
I like this nice concise answer although question whether the calculation for 7*24*60*60*1000 needed looking up in google!
spender
2010-02-02 19:15:15
@spender: It was the quickest way :)@invertedSpear: Whomever it was initially left a comment expressing his/her dissatisfaction with the typo, then immediately withdrew it while leaving the downvote.
Stiggler
2010-02-02 19:21:30
Downvote was due to a mis-read, sorry. It should be undone now.
GreenMatt
2010-02-02 19:25:50
Revise that last comment: I tried to undo it, but have been told it's too late unless you edit the answer again
GreenMatt
2010-02-02 19:32:04
+2
A:
Just my two cents. I don't like the idea, that the second answer assumes 52 weeks in a year, it will work for a single year, but is a solution to only this exact problem - eg. if you want to check the same thing moving back 10 years it won't work. I'd do it like this:
var today:Date = new Date();
// Here we store the day of the week
var currentDay:int = today.day;
trace (today);
const milisecondsInADay:uint = 1000*60*60*24;
// Here we move back a year, but we can just as well move back 10 years
// or 2 months
today.fullYear -= 1;
// Find the closest date that is the same day of the week as current day
today.time -= milisecondsInADay*(today.day-currentDay);
trace (today);
returns:
Tue Feb 2 21:13:18 GMT+0100 2010
Tue Feb 3 21:13:18 GMT+0100 2009
Robert Bak
2010-02-02 20:15:02
If you're going to say that, you might want to consider the leap seconds..
Timmy
2010-02-02 20:17:13
Sorry? I don't think I understand what you mean. 52 weeks equals 364 days. Which means that what you actually do is move the date forward a day or two. Here you actually use the actionscript date class to move back, and than look around the date it gives you.
Robert Bak
2010-02-02 20:28:03
Agreed, your answer looks to be cleaner than either mine or Stiggler's. In fact, I just realized my answer doesn't actually answer the original question...
Dan
2010-02-02 20:44:51