Delta UT1

Calculate difference between principal Universal Time (UT1) and Coordinated Universal Time (UTC) according to International Astronomical Union (IAU) 2000A reference system

  • Library:
  • Aerospace Blockset / Environment / Celestial Phenomena

    Aerospace Blockset / Utilities / Axes Transformations


The Delta UT1 block calculates the difference between principal UT1 and UTC according to the IAU 2000A reference system and Earth orientation data. By default, this block uses a prepopulated list of International Earth Rotation and Reference Systems Service (IERS) data. This list contains measured and calculated (predicted) data supplied by the IERS. The IERS measures and calculates this data for a set of predetermined dates. For dates after those listed in the prepopulated list, Delta UT1 calculates the data using this equation, limiting the values to +/- .9s:




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UT1 for UTC, specified as a modified Julian date. Use the mjuliandate function to convert the UTC date to a modified Julian date.

Data Types: double

Output Arguments

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Difference between UT1 and UTC.

Data Types: double


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Custom list of Earth orientation data, specified in a MAT-file.

Out-of-range action, specified as a string.

Action to take in case of out-of-range or predicted value dates, specified as a string:

  • Warning — Displays warning and indicates that the dates were out-of-range or predicted values.

  • Error — Displays error and indicates that the dates were out-of-range or predicted values.

  • None — Does not display warning or error.

Website or Earth orientation data file containing the Earth orientation data according to the IAU 2000A, specified as a website address or file name.

Folder for IERS data file, specified as a character array or string. Before running this function, create foldername with write permission.

To create the IERS data file in the destination folder, click the Create button.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Introduced in R2017b