Questions about Mathematica's date and time functions.
10
votes
2answers
421 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 This package now appears to be out of date; but as near as I can tell, many of the useful ...
16
votes
1answer
284 views
The Orbit and Perigee of the Flamsteed comet
Historical context
This year we have the 330-th anniversary of the Battle of Vienna - one of the great formative events of European history, it took place on September 12, 1683.
Kara Mustafa, Grand ...
6
votes
2answers
118 views
How can this AbsoluteTime call be made faster?
I need to convert tons of date strings into absolute times. This generates an example data set of 10,000 strings:
...
2
votes
1answer
74 views
ReadList importing negative times
This is probably an easy question to answer, but I need a fresh eye... I'm struggling with processing the following file (extract shown here) It's a list of dates, and positive/negative time durations ...
9
votes
1answer
140 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 ...
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 ...
12
votes
2answers
300 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 ...
6
votes
2answers
138 views
Select elements of list within a date range
I have a list which consists of elements each of which has a date in DateList format, a number and a flag (Y/N). e.g.
...
7
votes
3answers
235 views
Find all the last weekends in a year
In order to obtain the weekends of a year you'd use something like this:
...
6
votes
5answers
211 views
Handling holidays in financial time series
I have two lists: list1and list2, which are financial time series with only 2 variables—date and price. The problem is: these ...
9
votes
5answers
328 views
Sort date list in format DD/MM/YYYY
I have a list of dates (ranging from 2007 to 2012) in the DD/MM/YYYY format and I need to sort this list.
My problem is, when I simply use Sort[] I get:
...
1
vote
1answer
145 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]}
...
12
votes
1answer
184 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
...
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 ...
8
votes
1answer
195 views
How can I get the frame ticks from DateListPlot?
DateListPlot very nicely chooses major and minor frame tick and frame tick label/markers.
I am building a custom graphics function where either the ...
0
votes
1answer
82 views
Changing Datelist order
Im wondering how can I formulate a function which receives input in the string format "day.month.year hours: minutes: seconds" (for example, ...
9
votes
1answer
100 views
DateList not using current year when a year is not specified
According to the documentation when using DateList but not giving it a year it should use the current year. It is not doing that for me. Instead it uses 1900. ...
21
votes
0answers
385 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 ...
3
votes
2answers
98 views
Is there a faster way to compute the endpoint for a DateRange given the start, step, and length?
Say I am given a date start an increment step (possibly mixed radix) and a desired number of steps ...
1
vote
0answers
49 views
Is DateString supposed to be truncating seconds?
If I configure `` to format dates as ISO dates with
...
5
votes
2answers
193 views
2
votes
2answers
191 views
How do I generate a 3d histogram of runs
This question is an extension of the question I asked here Histogram of runs.
What I would like to do now is generate a Histogram3D that has the run duration on the x axis and the mean level on the ...
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;
...
4
votes
1answer
78 views
Strange behavior of DateList when converting string
DateList experiences some strange behavior which i cannot explain.
This code works fine:
...
1
vote
1answer
96 views
Working of Date[]
Date[] returns the current date of local system, Date[1] returns {2012, 11, 15, 17, 41, 0.3161629}, ...
7
votes
3answers
171 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;
...
10
votes
2answers
209 views
Approaches For Creating Cycle Plots in Mathematica
I am trying to create a cycle plot in Mathematica, and I am having a hard time finding the right approach to create the visualization. Can anyone give me a few pointers as to how to approach the ...
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 ...
18
votes
3answers
556 views
How can I make a heatmap of a days in year?
I know Mathematica has a ListPlot for time series but does it have a function for visualizing a list of dates as a heat map like this:
This idea is from D3, check it out here.
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
2answers
228 views
MovingAverage[] and Fit[] with data containing DateLists
I have data which has the following appearance: data = {{DateList, Real}, ..., {DateList, Real}}
It's easy to visualize the data by using ...
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
...
6
votes
3answers
122 views
Importing and manipulating strings - time data
I have a list of time durations, which are strings of the form: "hh:mm:ss". Here's a sample for you to play with:
...
9
votes
1answer
148 views
How can I convert the dates returned by FinancialData into decimal representation?
I'm trying to run a regression using Fit on the output of FinancialData["SPY", "Jan. 1, 2011"]. However, the dates returned ...
6
votes
3answers
209 views
Determining the dates of days
I'm trying to use WeatherData[] to give me (not sure how) the temperature, humidity, wind-speed, cloud cover... at a certain location.
I only want the information ...
6
votes
2answers
120 views
DateList Segmentation of data
I've been trying to separate large segments of DateList formatted data (years worth at a time) into individual days using the Split function.
The data has the form: ...
16
votes
9answers
928 views
Determining the week of a year from a given date
Consider the following:
AbsoluteTime["17/04/2012",{"Day","/","Month","Year"}];
From my calendar in my office, I know that April 17th is in the 16th week of the ...
4
votes
1answer
329 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 ...
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:
...
10
votes
7answers
176 views
7
votes
2answers
115 views
DatePlus and DateList are inconsistent with numerical handling of the final element
If you run this code you will see that DatePlus and DateList are inconsistent in the format of the lowest order element of the ...
5
votes
3answers
148 views
DateList's aggressive interpretation of TimeML duration codes
DateList "aggressively" interprets strings, such as "p72h":
DateList["p72h"] gives ...
5
votes
2answers
208 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 ...
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 ...
8
votes
1answer
163 views
Day of the week vs time on BoxWhiskerChart
I am completely stuck on how to approach this problem: I'm basically trying to figure out when is the best time to tweet on twitter, based on a list of timestamps:
Here are the raw values:
...
