Simulink DateTime

R2026b

Simulink® DateTime allows you to represent absolute calendar time, time standards, and epoch-based time in your model during simulation. This capability lets you model systems that depend on real-world time references, such as navigation, communication, and aerospace applications. You can:

  • Represent and manipulate absolute date and time values in Simulink signals.

  • Convert among multiple time standards, such as UTC an TAI.

  • Account for leap seconds in time-critical simulations.

  • Map simulation time to real-world calendar dates.

This table lists the Simulink DateTime blocks.

DescriptionBlock

Output current simulation calendar date and time as DateTime signal

DateTime Clock

Convert time points or storage data types of DateTime signal

DateTime Data Type Converter

Convert between DateTime time standards

DateTime Time Standard Converter

Convert DateTime signal to calendar time format

DateTime to Calendar Time

Convert DateTime signal to formatted string

DateTime to Formatted String

Extract value of DateTime input signal

From DateTime

Output DateTime signal

To DateTime

Simulink blocks might use Simulink.DateTimeType objects to specify the time point, time standard, and storage data type of DateTime signals.

Simulink DateTime Concepts

This table lists concepts and terminology for Simulink DateTime.

TermDefinition

Calendar time

DateTime representation year, month, day, hour, minute, second.

Epoch

Reference point in time from which elapsed time is measured, for example, seconds since Unix epoch (1970-01-01T00:00:00 UTC).

Epoch time

DateTime representation expressed as elapsed time since a defined epoch.

Leap second

One-second adjustment occasionally applied to UTC to maintain alignment with Earth rotation.

Simulink DateTime models handle leap seconds explicitly because these seconds affect conversions between UTC and continuous time standards (TAI).

  • When you convert to or from UTC, the model uses a leap second table to determine the correct offset at any given date.

  • During a leap second event, UTC signals can represent the value 23:59:60.

Time representation

A DateTime value encodes the elapsed time from a reference epoch, which you can configure based on your application domain.

  • Simulink DateTime values carry both a numeric time value and metadata about the time standard and epoch.

  • Simulink DateTime supports multiple epoch choices to align with industry conventions (for example, J2000 (January 1, 2000, 12:00:00 Terrestrial Time (TT)), UNIX® epoch).

Time standard

Defines the rules for measuring the passage of time. Simulink DateTime supports multiple time standards and provides conversion between them.

  • UTC — Coordinated Universal Time; incorporates leap seconds

  • TAI — International Atomic Time; continuous, differs from UTC by accumulated leap seconds

  • TT — Terrestial Time, exactly 32.184 seconds ahead of International Atomic Time (TAI)

You convert between time standards using the DateTime Time Standard Converter block.

Time zone

Regional offset from UTC used to express local civil time. Time zone handling allows you to express DateTime values in local time.

Design considerations include daylight saving time transitions and the relationship between time zones and UTC offsets.

DateTime Type

DateTime blocks create and use DateTimeType data types as needed, for example, when a block outputs a DateTime signal. Simulink blocks might use Simulink.DateTimeType objects to specify the time point, time standard, and storage data type of DateTime signals. On signal lines, DateTime signals appear as datetime(timeStandard).

To create DateTime data types for blocks that support DateTime, you can:

Relationship to MATLAB datetime Data

While datetime data operates in the MATLAB® workspace, Simulink DateTime provides an in-model representation suitable for signal flow, code generation, and real-time execution.

The Simulink DateTime blocks work with MATLAB datetime data with the DateTime Clock block and the Date and time at simulation time zero configuration parameter.

  • Date and time at simulation time zero model configuration parameter — To specify the date and time at simulation time zero at the model level using the datetime object, set the Date and time at simulation time zero model configuration parameter. If the block Date and time at simulation time zero value differs from the value of the Date and time at simulation time zero model configuration parameter, the block value takes precedence.

  • DateTime Clock block — To set the date and time at simulation time zero at the block level, set the Initial date and time source parameter to Specify value. And then, In the Date and time at simulation time zero parameter, specify the datetime object. If the block Date and time at simulation time zero value differs from the value of the Date and time at simulation time zero model configuration parameter, the block value takes precedence.

  • Simulink converts MATLAB datetime data to the configured DateTime representation of the model.

  • When loading timeseries input data with datetime row times, interpolation must be turned off.

Simulink Blocks That Support DateTime Data Types

These blocks support DateTime data types:

You can assign DateTime-specific data types to signals in Simulink models. These types carry time standard and epoch metadata alongside the numeric value. To create DateTime data types, use the Simulink.DateTimeType object.

Signal Representation

DateTime signals in Simulink carry the time value and associated metadata.

  • UTC signals might combine the datetime numeric value with a leap second indicator to unambiguously represent times during or near a leap second event.

  • This composite representation enables 23:59:60 to be distinguished from 00:00:00 of the next day.

Rounding Timestamp Values

Simulink DateTime blocks always round timestamps, including negative timestamps, down using the concept of floor rounding. Floor rounding is the act of taking the largest value that is less than or equal to the original value. Applying this concept, at time t = -4.5 seconds with respect to midnight, a clock with second precision reads 11:59:55 PM.

DateTime Signals

To introduce DateTime values into your model, use a DateTime Clock block or load datetime data from the MATLAB workspace.

  • The DateTime Clock block generates a continuously advancing DateTime signal.

  • You can supply DateTime values through input ports using MATLAB datetime data stored in a timeseries or timetable.

Use the DateTime Clock block to create DateTime signals and have the Display block display the output. In this model, the Date and time at simulation time zero parameter of the DateTime Clock block is set to datetime(2000,1,1,0,0,0).

DateTime Clock output of 01-Jan-2000 00:00:10

Manipulate DateTime Values

Common operations on DateTime values include:

  • Convert between time standards — Use the DateTime Time Standard Converter block to transform DateTime values among supported time standards, including UTC, TAI, and TT.

    Use the DateTime Clock block to create DateTime signals and have the DateTime Standard Converter block convert the DateTime UTC signal to a TAI signal. In this model:

    • The Date and time at simulation time zero parameter of the DateTime Clock block is set to datetime(2000,1,1,0,0,0).

    • The Account for new leap seconds after simulation start parameter of the DateTime Clock block is cleared.

    • The Sample time parameter of the DateTime Clock block is set to 1 for discrete behavior.

    • The Time standard conversion parameter of the DateTime Time Standard Converter block is set to UTC to TAI.

    DateTime Clock UTC time converted to TAI time using DateTime Time Standard Converter block.

  • Extract DateTime signal to calendar components — To extract year, month, day, hour, minute, and second from a DateTime signal, use the DateTime to Calendar Time block.

    Use the DateTime Clock block to create DateTime signals and have the DateTime to Calendar Time block extract the calendar components from the DateTime signal. In this model:

    • The Date and time at simulation time zero parameter of the DateTime Clock block is set to datetime(2000,1,1,0,0,0).

    • The Account for new leap seconds after simulation start parameter of the DateTime Clock block is cleared.

    • The Sample time parameter of the DateTime Clock block is set to 1 for discrete behavior.

    • Connect the DateTime to Calendar Time block output ports to multiple Display blocks, one per output port.

    DateTime Clock to calendar time using DateTime to Calendar Time block

  • Format DateTime signal as strings — To display DateTime signals as time strings, use the DateTime to Formatted String block.

    To the previous DateTime Standard Converter model, add DateTime to Formatted String block and Display blocks.

    DateTime Clock UTC time converted to TAI time using DateTime Time Standard Converter block and then datetime is converted to string and displayed.

Logging

You can log DateTime signals to the MATLAB workspace as MATLAB datetime data stored in a timeseries or timetable. The row times of a logged timetable represent simulation times, while DateTime signals appear as data columns of type datetime.

Visualization with Scopes

When visualizing DateTime signals on Scope blocks, simulations that use DateTime can be visualized on scopes with calendar-formatted time values on the T-axis.

Loading Data

Simulink DateTime supports root inport loading.

Log, Load, and Visualize DateTime Data

Open Live Script

This example shows how to log, load, and visualize DateTime signals in Simulink.

Visualize and Log DateTime Data From Simulation

Load model ex_datetime_generate_data.slx. Set model configuration parameter Date and time at simulation time zero to July 19, 2026.

modelA = 'ex_datetime_generate_data';
open_system(modelA)
set_param(modelA, 'DateTimeAtSimulationTimeZero', 'datetime(2026,7,19,TimeStandard=''UTC'')');

Run the model and examine the output data in the Scope. The DateTime Clock block outputs a Julian date whose day number increases by 1 over the course of the simulation. The Scope plots the DateTime signal using its stored value, which is the numerical value of the Julian date. The Scope T-Axis is labeled with dates and times starting at July 19, 2026.

out = sim(modelA);
open_system([modelA '/Scope'])

Save the logged output data to a new workspace variable and examine it. The data is logged as a timeseries of MATLAB datetime objects.

ts_data = out.yout{1}.Values
  timeseries

  Common Properties:
            Name: ''
            Time: [51x1 double]
        TimeInfo: [1x1 tsdata.timemetadata]
            Data: [51x1 datetime]
        DataInfo: [1x1 tsdata.datametadata]

  More properties, Methods

Load DateTime Data in Another Model and Visualize It

Load model ex_datetime_compare_data.slx. Set model configuration parameter Date and time at simulation time zero to July 20, 2026.

modelB = 'ex_datetime_compare_data';
open_system(modelB)
set_param(modelB, 'DateTimeAtSimulationTimeZero', 'datetime(2026,7,20,TimeStandard=''UTC'')');

Configure the model root input port to load the logged workspace data of the previous model.

set_param(modelB, 'LoadExternalInput', 'on', 'ExternalInput', 'ts_data');

Run the model and examine both output signals in the Scope. The two plotted Julian date signals differ in stored value by exactly 1. The Scope T-Axis is labeled with dates and times starting at July 20, 2026.

sim(modelB);
open_system([modelB '/Scope'])

Bus and Structure Integration

You can include DateTime values as elements in Simulink bus signals and structures.

  • A bus element can have a DateTime data type.

  • In generated code, DateTime bus elements map to structure fields with the appropriate storage type.

Replace DateTime Clock Block with System Time Call

This example uses:

Open Live Script

This example shows how to use a code replacement library (CRL) entry to replace a DateTime Clock block with a call to system time provided by the C <time.h> header.

Prepare Model

Open model ex_datetimeclock_crl_harness.slx. This model uses an ERT-based system target file, and it includes a Model block configured for SIL simulation. The referenced model ex_datetimeclock_crl_model.slx contains the DateTime Clock block to be replaced by a call to the systemTime function in the generated code.

topModel = 'ex_datetimeclock_crl_harness';
botModel = 'ex_datetimeclock_crl_model';
open_system(topModel)
load_system(botModel)

Examine C Implementation

Examine the provided C implementation of the systemTime function.

type systemTime.h
/* Copyright 2026 The MathWorks, Inc. */
int systemTime();

type systemTime.c
/* Copyright 2026 The MathWorks, Inc. */
#include "systemTime.h"
#include <time.h>

int systemTime()
{
    return time(NULL);
}

Prepare Code Replacement Library

Examine the code replacement library, which is created in crl_datetimeclock_systemtime.m and registered in rtwTargetInfo.m. The entry in the library specifies the getDateTime key and the types of two input arguments. u1 is an int32 that contains the block's output at simulation time 0, while u2 is a double that contains the current simulation time. Both arguments are ignored by the systemTime implementation. The entry also specifies the block TimePoint and TimeStandard to match by setting those algorithm parameters.

type crl_datetimeclock_systemtime.m
function hLib = crl_datetimeclock_systemtime
% CRL_DATETIMECLOCK_SYSTEMTIME - Create a Code Replacement Library entry
% to replace a DateTime Clock block with a call to system time from the C
% <time> library.

%   Copyright 2026 The MathWorks, Inc.

hLib = RTW.TflTable;

hEnt = createCRLEntry(hLib, ...
    'int32 y1 = getDateTime(int32 u1, double u2)', ...
    'int32 y1 = systemTime()');

hEnt.setTflCFunctionEntryParameters( ...
    'Priority', 100, ...
    'ImplementationHeaderFile', 'systemTime.h', ...
    'ImplementationHeaderPath', '.', ...
    'ImplementationSourceFile', 'systemTime.c', ...
    'ImplementationSourcePath', '.');

algParams = getAlgorithmParameters(hEnt);
algParams.TimePoint = 'Seconds since Unix epoch';
algParams.TimeStandard = 'UTC';
setAlgorithmParameters(hEnt, algParams);

hLib.addEntry(hEnt);

end

if isfile("rtwTargetInfo.m")
    delete rtwTargetInfo.m
end
copyfile DateTimeClockRtwTargetInfo.txt rtwTargetInfo.m
type rtwTargetInfo.m
function rtwTargetInfo(cm)

cm.registerTargetInfo(@loc_register_crl);

end

function this = loc_register_crl

% Register a code replacement library for use with ex_datetimeclock_crl_model
this(1) = RTW.TflRegistry;
this(1).Name = 'DateTime Clock CRL';
this(1).TableList = {'crl_datetimeclock_systemtime'};
this(1).BaseTfl = '';
this(1).TargetHWDeviceType = {'*'};
this(1).Description = '';

end

Add Code Replacement Library

Add the code replacement library to the referenced model and run the harness model. Ignore warnings caused by unsaved model changes.

set_param(botModel, 'CodeReplacementLibrary', 'DateTime Clock CRL');
warning('off', 'Simulink:slbuild:unsavedMdlRefsAllowed')
sl_refresh_customizations;
simout = sim(topModel);
### Searching for referenced models in model 'ex_datetimeclock_crl_harness'.
### Total of 1 models to build.
### Starting serial code generation build.
### Starting model reference code generation target build for: ex_datetimeclock_crl_model
### Successful completion of build procedure for: ex_datetimeclock_crl_model

Build Summary

Model reference code generation targets:

Model                       Build Reason                                          Status                        Build Duration
==============================================================================================================================
ex_datetimeclock_crl_model  Target (ex_datetimeclock_crl_model.c) did not exist.  Code generated and compiled.  0h 0m 6.1239s

1 of 1 models built (0 models already up to date)
Build duration: 0h 0m 7.3431s
### Preparing to start SIL simulation ...
Building with 'gcc'.
MEX completed successfully.
### Starting SIL simulation for component: ex_datetimeclock_crl_model
### Application stopped
### Stopping SIL simulation for component: ex_datetimeclock_crl_model

Simulate and Examine Results

Compare the logged output of the Simulink model to the date and time reported by MATLAB's datetime('now') command.

tMATLAB = datetime('now', TimeStandard='UTC', Format='uuuu-MM-dd''T''HH:mm:ss''Z''');
tSimulink = datetime(simout.yout{1}.Values.Data(1), Format='uuuu-MM-dd''T''HH:mm:ss''Z''');

fprintf('MATLAB system time is %s\n', tMATLAB)
MATLAB system time is 2026-08-07T09:05:26Z

fprintf('Simulink model output is %s\n', tSimulink)
Simulink model output is 2026-08-07T09:05:26Z

Limitations

  • The Date and time at simulation time zero configuration parameter cannot be set to a time earlier than January 1, 1972.

  • Simulink DateTime cannot represent data in non-UTC time zones.

  • Simulink does not support DateTime signals earlier than January 1, 1400 or later than December 31, 9999.

  • The DateTime Clock block is not supported in export-function models.

  • DateTime Clock blocks are not supported in subsystems that model Simulink based states in Stateflow®.

See Also

Blocks

Objects

Model Settings