# Comparing Stop/Start Dates and Times with LLTK

Lab scientists need to record both a start and stop date/time for an incubation. As a second evaluation of how many hours the incubation lasted, the scientists want BaseSpace Clarity LIMS to calculate the elapsed time.

The Lab Logic Toolkit *evaluateDynamicExpression* script can compare date/time entries and calculate elapsed hours. As *Date* fields in the LIMS do not display the required time component for this calculation, *Text* fields are needed.

The bash command uses a 'Date' function to convert the *Text* date/time entries into dates, and also uses a 'getTime' method to convert those dates into milliseconds since 1 January 1970 00:00:00 UTC. The difference between the two converted entries is then changed from milliseconds to hours.

## Example

1. Create a step level *Text* field for the *Start Date/Time*.
   * In this example, the field is named *Incubation Start yyyy-mm-dd hh24:mi*. The format is included in the name to assist the scientist entering the date/time.
2. Create a step level *Text* field for the *Stop Date/Time*.
   * In this example, the field is named *Incubation Stop yyyy-mm-dd hh24:mi*.
3. Create a step level *Numeric* field for the *Incubation Hours*. Set your preferred decimal place limit.
4. Create an automation and enter the following command line (if you have used different field names, edit the example command line to match):

   <pre class="language-markup" data-overflow="wrap"><code class="lang-markup">bash -l -c "/opt/gls/clarity/bin/java -jar /opt/gls/clarity/extensions/ngs-common/v5/EPP/ngs-extensions.jar -i {stepURI:v2} -u {username} -p {password} script:evaluateDynamicExpression 
   -exp 'step.::Incubation Hours:: = (Date.parse(::yyyy-mm-dd H:m::, step.::Incubation Stop yyyy-mm-dd hh24:mi::).getTime() - Date.parse(::yyyy-mm-dd H:m::, step.::Incubation Start yyyy-mm-dd hh24:mi::).getTime()) / (1000*60*60)' -log {compoundOutputFileLuid0}"
   </code></pre>
5. Set the automation to be triggered by a button on the step. This allows the scientist to enter/edit the *Start* and *Stop Date/Time* before the elapsed hours are calculated.

   > ℹ Adjustment for the *Start/Stop* events taking place over the 'daylight savings change events' is not included in this example.

**If you want to use a button to populate a Text field with the current date/time, then use:**

{% code overflow="wrap" %}

```markup
bash -l -c "/opt/gls/clarity/bin/java -jar /opt/gls/clarity/extensions/ngs-common/v5/EPP/ngs-extensions.jar -i {stepURI:v2} -u {username} -p {password} script:evaluateDynamicExpression -exp 'step.::Formulation:: = new Date().getDateTimeString()' -log {compoundOutputFileLuid0}"
```

{% endcode %}