Questions about Mathematica's date and time functions.
22
votes
6answers
773 views
Faster alternatives for DayOfWeek
It has been noticed on several occasions that DayOfWeek function is rather slow when applied to a large list of dates, e.g. in this recent question. What faster ...
10
votes
3answers
316 views
Simpler way to fill date gaps with zero values
One basic problem when working with data like sales and dates is the case where you dont't have sales in all days, so you have to fill it to take information as average or to make a plot. See this toy ...
8
votes
3answers
236 views
Faster Alternatives to DateDifference
I need a faster implementation of FractionOfYear and FractionOfMonth, which do the following:
Input: A time/date specified by ...
5
votes
2answers
207 views
From a list of dates get a list of the last date available in a each month
I wondered if anyone has another or even a more direct way of finding the last dates of each month available from a list of successive dates?
I currently do the following (note: nothing special about ...
12
votes
1answer
183 views
Is there a way to get AbsoluteTime to correctly report absolute time differences?
Absolute time supposedly reports the "total number of seconds" between two dates, but it does not. For example because of the leap second applied at 2012-06-30T23:59:60Z
...
12
votes
2answers
299 views
How is AstronomicalData interpreting its date arguments?
It is easy to confirm that the AstronomicalData is not interpreting its arguments as UTC (or "GMT", which is, in any case, ambiguous) dates by verifying that the ...
5
votes
2answers
192 views
10
votes
2answers
412 views
How do I compute sidereal time and JD?
There was once a package that provided a wide range of functions for computing astronomical information. This package now appears to be out of date; but as near as I can tell, many of the useful ...
21
votes
0answers
384 views
What calendar is Mathematica using for dates in the distant past?
It appears that Mathematica treats all dates as proleptic Gregorian dates by default, a hypothesis that can be easily tested by using AbsoluteTime to compute the ...
9
votes
1answer
138 views
Why do DateList, DateString, and AstronomicalData ignore $TimeZone?
My reading of the documentation for DateList and DateString lead me to believe that both functions use ...
9
votes
1answer
160 views
How do I determine astronomical transit times?
Mathematica, through the "legacy" Scientific Astronomer package, used to have the ability to easily determine accurate transit times of astronomical objects simply, with ...
9
votes
1answer
341 views
How to import date (YYYY-MM-DD) data from a file?
I have a file with data in form {date, value}:
2010-05-19 17
2010-05-20 20
...
4
votes
1answer
328 views
Simple countdown timer in Mathematica
I dug around a bit and did not find a simple and clear implementation of countdown stopwatch in Mathematica. I am looking for a function that takes as an input a certain integer and then counts down ...
2
votes
1answer
66 views
Is it safe to change the value of $TimeZone?
I'd like to configure some of my notebooks to assume all calculations using dates, times and locations (notably AstronomicalData , but others too) take place at the ...
1
vote
1answer
142 views
Converting Excel serial dates with NETLink
Excel serial dates are not straightforward to convert since they include non-existent dates, e.g.
{DatePlus[{1990, 1, 0}, 59], DatePlus[{1990, 1, 0}, 60]}
...
7
votes
3answers
170 views
Filter list based on date
What I would like to do is remove entries from a list of instrument data when it is in maintenance. The maintenance data I have is a series of dates which look like this;
...
2
votes
2answers
248 views
Histogram of runs
What I would like to do is generate a histogram of the consecutive time spent under a level. For example if the level I was interested in was 1.0 and I had this data;
...
1
vote
1answer
170 views
How can Time be made to go backwards?
I would like to make a countdown timer, but cannot find a reliable method to make the DateList[] function reverse.
The not so robust code for the Digital Clock with the display of seconds follows:
...
