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Questions tagged [date-math]

Questions about performing arithmetic operations on dates and times.

129 questions
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Rails 3 Calculate age of embedded records

I'm using mongodb, and have a model that adds comments as embedded documents. How do I get the average age of comments for an entry? (relative example, my fields vary a little) So I can have many comments for an entry, and I need to find out the…
Kevin Brown
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Making NSTimeZone Trouble Free in Unit Tests

So here's the problem with doing unit tests of calendar code in Objective-C: the Timezone contains the information about daylight savings, so you write a test in the summer, expecting sunrise on June 10th to occur at 6:02 am. Your test passes,…
Rob
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Subtract months from a given date

I need to subtract months from a given DateCol in a matrix. I was using the command bsxfun(@minus, datevec(date),[0,3,0,0,0,0]) to subtract 3 months from the given date. You can see there is a bug in this code. If the date is 1-Feb-2011, this…
Maddy
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Calculating number of Quarters between 2 dates in DAX, applying filter

I have the following table, tbl_Episodes (10K records): ClientID AdmDate DischDate 54 9/20/2013 5/28/2015 63 3/07/2013 4/12/2014 75 4/07/2014 12/31/2050 . …
Hell-1931
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Find the nearest overlap between given time series

I'm building a scheduling system where I store an initial appointment and how often it repeats. My table looks something like this: CREATE TABLE ( id serial primary key, initial_timestamp timestamp not null, recurring interval ); id …
Jaden Baptista
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Round-trip conversion of a System.DateTime instance via a Unix time stamp is off by 1 hour

Note: For convenience, PowerShell is used to demonstrate the behavior, but the question is about surprising behavior of the System.DateTime .NET type, contrasted with type System.DateTimeOffset. There may be a good conceptual reason for this…
mklement0
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please explain my error in this javascript date math

Here's the output from the Visual Studio Immediate Window. I start with mondaysDate, create a second date, thisDate, and then add integers to it using mondaysDate as the base. I don't understand why adding 3 to the date yields November 2 and adding…
Tim
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Comparing SQL date without current month

I have a table in Access with string columns and a date column. I want to get all the rows from the table when the date is lower than 22.10.2010, except this month. So, i need the rows from 30.09.2010 to ... I tied something, but I figured out it's…
DaJackal
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Oracle downtime in minutes per month

This is written in Oracle 11g or 12c... Hello, I am attempting to shape this data into hours of downtime for the previous 12 months, shaped this way to support a graph. In the Oracle SQL query below, the commented query "M" shows how to put in one…
SMerrill8
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PHP strtotime Issue with date differences

Anyone can explain me what is wrong with strtotime function in this example? I'm trying to count differences between dates. PHP 5.6.0 (cli) (built: Aug 28 2014 08:03:51) When i execute this loop it displays number 88…
MEAT
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Best practice for PHP/MySQL Appointment/Booking system

I need some people to battle a "best practice" for a PHP/MySQL appointment system for a hairdresser I'm currently working on. Hopefully, together we can clear some things up to avoid having to re-do the system afterwards. I've been looking at SO and…
Joshua - Pendo
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Find only particular days between two dates

I have an Oracle table with data like below: 1. ID DATE 2. 12 02/11/2013 3. 12 02/12/2013 4. 13 02/11/2013 5. 13 02/12/2013 6. 13 02/13/2013 7. 13 02/14/2013 8. 14 …
user2089954
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Date manipulation in PHP

I am trying to repeat the date by a month for a fixed number of times in a loop. It will only echo the date if the date is a valid date otherwise it will skip the date. For example if the "2012-02-30 10:10:00" is coming in the loop it will be…
Nihilarian
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PHP Date Subtract Only works first iteration of Do While Loop

I have mySQL tables that are suffixed with 'mmdd'. I need to iterate through and store this 'mmdd' value in an array as I get a hit on the table. The problem is that the date subtract of 1 day only works on the 1st iteration. I have tried this many…
user1341613
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How can i parse a date to same day of previous month?

How can i parse a date to same day of previous month in PHP? Example: input Output 2018-07-25 -> 2018-06-25 2018-07-31 -> 2018-06-30 (because there is no 31) My code $d = "2018-07-25"; $xd =…
Rafeeq Mohamed
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