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MidDate
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MidDate

New in 14.2

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MidDate[datespec]

gives the midpoint instant of a date or list of dates datespec.

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MidDate[datespec,gran]

gives the midpoint date object with granularity gran.

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MidDate[datespec,gran,x]

gives the date that is the fraction x between the beginning and end of datespec.

Details and Options

  • MidDate gives the date that is midway through a given date or list of dates.
  • Possible forms of datespec in MidDate[datespec,…] include:
  • DateObject[…]mid date of a date object of any granularity
    TimeObject[…]mid time of a time object of any granularity
    DateInterval[…]mid date of a date interval
    {d1,d2,…}mid date of a list of dates, times and intervals
    TimeSeries[…]mid date of the times of a time series
    EventSeries[…]mid date of the times of an event series
    TemporalData[…]mid date of the times of temporal data
  • MidDate[(d1,d2,…}] gives the midpoint instant based on the sum of probability density functions for a uniform distribution of the di dates.
  • MidDate takes the following options:
  • CalendarType Automaticcalendar for generated date
    DateFormat Automaticformat used to display date
    DateGranularityAutomaticcalendar granularity for generated date
    Method Automaticmidpoint detection method
    TimeSystem Automatictime system being used
    TimeZone Automatictime zone being used
  • With MidDate[{d1,d2,…},Methodmethod], the Method option value method determines how midpoint dates are calculated for the di dates. Possible Method values include:
  • "GranularMean"mean weighted by granularity length (default)
    "GranularMedian"median weighted by granularity length
    "WeightedMean"mean weighted by full duration of each date
    "UnionedMean"mean of the unioned region of all dates
    "MidpointMean"mean of midpoints
    "MidpointMedian"median of midpoints
    "BoundsMean"mean of the date bounds

Examples

open allclose all

Basic Examples  (4)Summary of the most common use cases

Get the midpoint instant for a month-granular date:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-ppn0uf
Out[1]=1

Find the day that falls in the middle of a year:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-2hziip
Out[1]=1

Find the hour that is 2/3 of the way through a given week:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-s9e0xz
Out[1]=1

Find the mid date of three instants in the year 2024:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-03yf3o
Out[1]=1

Scope  (7)Survey of the scope of standard use cases

For list inputs, the midpoint is taken based on the implicit interval for each date in the list:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-pwon6h
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-odwg27
Out[2]=2

The full time interval for each date is taken into account:

In[3]:=3
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https://wolfram.com/xid/0enxc2jv4-b94rbu
Out[3]=3

For mid dates with coarse granularity, the date given corresponds to the instance that encompasses the midpoint, even if it begins before the first date:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-qmdmic
Out[1]=1

Get the mid date for an EventSeries:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-hwc1fs
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-lsix7z
Out[2]=2

Get the mid date from a Databin:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-01s3kr
Out[1]=1

Find the mid date for an Association:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-j73bb9
Out[1]=1

Find the mid time of five times today:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-vhym9o
Out[1]=1

Find the midpoint instant of three date intervals:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-sq4sl1
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-zor1ck
Out[2]=2

Options  (9)Common values & functionality for each option

CalendarType  (1)

Return the midpoint date in the Japanese calendar:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-z3uidz
Out[1]=1

DateFormat  (1)

Return the midpoint date in an "ISODateTime" format:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-m9xm76
Out[1]=1

Method  (5)

The default midpoint detection method ("GranularMean") takes into account granularity length when selecting a midpoint:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-8mg5gk
Out[1]=1

This means a one-week period is weighted equally whether it appears as a single "Week" date or as a sequence of seven "Day" dates:

In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-2f3e9
Out[2]=2

The method "WeightedMean" takes into account the full length of each date, not just its granularity:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-58y2rg
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-whziig
Out[2]=2

The method "MidpointMedian" gives equal weight to all dates, regardless of granularity:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-5bkfq
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-xfdp9
Out[2]=2

The method "BoundsMean" considers only the outer date bounds of the dates:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-pwc7jf
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-pm4tga
Out[2]=2

Some midpoint detection methods weight for granularity, while others treat all dates as equally weighted:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-8dlpvg
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-wxbgh4
In[3]:=3
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https://wolfram.com/xid/0enxc2jv4-lcyyeo
In[4]:=4
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https://wolfram.com/xid/0enxc2jv4-1cddjx

With only two dates given, "Weighted" methods will account for granularity and be pulled toward coarser granularity dates:

In[5]:=5
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https://wolfram.com/xid/0enxc2jv4-wzx9ih
Out[5]=5

With the coarser granularity broken up into individual dates, the "Weighted" methods remain consistent:

In[6]:=6
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https://wolfram.com/xid/0enxc2jv4-7oj7zj
Out[6]=6

Midpoint methods weight all dates equally and thus do not account for difference in granularity:

In[7]:=7
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https://wolfram.com/xid/0enxc2jv4-8b1dd6
Out[7]=7

If broken into individual days, these midpoint methods will be pulled to the right:

In[8]:=8
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https://wolfram.com/xid/0enxc2jv4-lv44q3
Out[8]=8

"WeightedMean" and "UnionedMean" both account for the full duration of dates, but "WeightedMean" will account for overlapping intervals, while "UnionedMean" will flatten all intervals:

In[9]:=9
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https://wolfram.com/xid/0enxc2jv4-oh3be9
In[10]:=10
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https://wolfram.com/xid/0enxc2jv4-rgzoc2
In[11]:=11
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https://wolfram.com/xid/0enxc2jv4-znnwzb
Out[11]=11

TimeSystem  (1)

Return the midpoint date in the "TAI" time system:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-e8v2kl
Out[1]=1

TimeZone  (1)

Return the midpoint date in GMT:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-2hvgqd
Out[1]=1

Applications  (1)Sample problems that can be solved with this function

Find the release dates of all James Bond movies:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-6v9c8t
Out[1]=1

Find the mid date of those release dates:

In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-8f5vp3
Out[2]=2

The midpoint of the bounds was six years later, reflecting an accumulation of releases in the early years:

In[3]:=3
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https://wolfram.com/xid/0enxc2jv4-2xdwpm
Out[3]=3

Properties & Relations  (1)Properties of the function, and connections to other functions

Mean, Median, Quantile and CentralFeature all use different methods to find central dates:

In[1]:=1
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https://wolfram.com/xid/0enxc2jv4-5nxs0h
In[2]:=2
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https://wolfram.com/xid/0enxc2jv4-tfuayo
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0enxc2jv4-37hhlb
Out[3]=3
In[4]:=4
✖
https://wolfram.com/xid/0enxc2jv4-xlioa8
Out[4]=4
In[5]:=5
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https://wolfram.com/xid/0enxc2jv4-ponlad
Out[5]=5

Possible Issues  (1)Common pitfalls and unexpected behavior

A list of numbers is interpreted by MidDate as a list of absolute times, not as a single date list:

In[1]:=1
✖
https://wolfram.com/xid/0enxc2jv4-kzt21g
Out[1]=1
In[7]:=7
✖
https://wolfram.com/xid/0enxc2jv4-k7jutq
Out[7]=7
In[3]:=3
✖
https://wolfram.com/xid/0enxc2jv4-6ebsag
Out[3]=3
Wolfram Research (2025), MidDate, Wolfram Language function, https://reference.wolfram.com/language/ref/MidDate.html.
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Wolfram Research (2025), MidDate, Wolfram Language function, https://reference.wolfram.com/language/ref/MidDate.html.

Text

Wolfram Research (2025), MidDate, Wolfram Language function, https://reference.wolfram.com/language/ref/MidDate.html.

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Wolfram Research (2025), MidDate, Wolfram Language function, https://reference.wolfram.com/language/ref/MidDate.html.

CMS

Wolfram Language. 2025. "MidDate." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/MidDate.html.

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Wolfram Language. 2025. "MidDate." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/MidDate.html.

APA

Wolfram Language. (2025). MidDate. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MidDate.html

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Wolfram Language. (2025). MidDate. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MidDate.html

BibTeX

@misc{reference.wolfram_2025_middate, author="Wolfram Research", title="{MidDate}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/MidDate.html}", note=[Accessed: 19-June-2025 ]}

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@misc{reference.wolfram_2025_middate, author="Wolfram Research", title="{MidDate}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/MidDate.html}", note=[Accessed: 19-June-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_middate, organization={Wolfram Research}, title={MidDate}, year={2025}, url={https://reference.wolfram.com/language/ref/MidDate.html}, note=[Accessed: 19-June-2025 ]}

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@online{reference.wolfram_2025_middate, organization={Wolfram Research}, title={MidDate}, year={2025}, url={https://reference.wolfram.com/language/ref/MidDate.html}, note=[Accessed: 19-June-2025 ]}