# Date/time synthesis options

When you select the **Synthesize** option for Date/Time values, you can either:

* Shift the date within a specific range.
* Truncate all dates to January 1. The year is set based on whether the original year is more than 89 years ago.

You can also configure how to handle dates that Textual does not recognize, and add additional date formats for Textual to recognize.

<figure><img src="/files/rfzjSFu6qtlHMntdFoy6" alt=""><figcaption><p>Datetime synthesis options</p></figcaption></figure>

## Shifting the date within a range

To shift the date within a specified range:

1. From the Generator type dropdown list, select **Date shift generator**.
2. In the **Left bound on # of Days To Shift** field, enter the number of days before the original date within which the replacement datetime value must occur.\
   \
   For example, if you enter `10`, then the replacement datetime value cannot occur earlier than 10 days before the original value.
3. In the **Right bound on # of Days To Shift** field, enter the number of days after the original date within which the replacement datetime value must occur.\
   \
   For example, if you enter `6`, then the replacement datetime value cannot occur later than 6 days after the original value.
4. To apply the same shift to all datetime values within a given file, check the **Apply same shift for entire document** checkbox. For example, if this is checked, Textual might shift all datetime values in a file 3 days into the future.

## Truncating the date

To truncate the date, from the **Generator Type** dropdown list, select **Date Truncation Generator**.

With this option, in the output:

* The month and day are always January 1.
* If the original year is less than 90 years ago, then the year remains as is in the output.
* If the original year is 90 years or more ago, then the year is set to the current year minus 89.

## Selecting how to handle invalid values <a href="#synthesis-options-datetime-unrecognized-formats" id="synthesis-options-datetime-unrecognized-formats"></a>

Textual can parse datetime values that use either a format in [Default supported datetime formats](/textual/dataset-configure-redaction/textual-datasets-synthesis-options/synthesis-options-for-specific-entity-types/default-datetime-formats.md) or a format that you add.

The **Scramble Unrecognized Dates** checkbox indicates how Textual should handle datetime values that it does not recognize.

By default, the checkbox is checked, and Textual scrambles those values.

To instead pass through the values without changing them, uncheck **Scramble Unrecognized Dates**.&#x20;

## Adding datetime formats

By default, Textual is able to recognize datetime values that use a format from [Default supported datetime formats](/textual/dataset-configure-redaction/textual-datasets-synthesis-options/synthesis-options-for-specific-entity-types/default-datetime-formats.md).

Under **Additional Date Formats**, you can add other datetime formats that you know are present in your data.

The formats must use a [Noda Time LocalDateTime pattern](https://nodatime.org/1.4.x/userguide/localdatetime-patterns).

To add a format, type the format in the field, then click **+**.

To remove a format, click its delete icon.


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