# Incorrect date format

<table><thead><tr><th width="138">Check ID</th><th>MF_0001</th></tr></thead><tbody><tr><td>Category</td><td>Quality</td></tr><tr><td>Summary</td><td>Mendix uses <a href="https://docs.mendix.com/refguide/parse-and-format-date-function-calls/">letter patterns</a> for formatting date strings. The letters used when configuring these patterns can be confusing. This can lead to dates that are incorrectly formatted. This check looks for common mistakes made when configuring date formats.</td></tr><tr><td>Options</td><td>This check does not have any options.</td></tr><tr><td>Pass</td><td>Date format expressions in your microflow do not contain any common mistakes.</td></tr><tr><td>Fail</td><td><p>Date format expressions in your microflow contain common mistakes such as (all examples below show FAIL conditions):<br><br><strong>Day of year should not be used in parse/format date time functions</strong><br><code>parseDateTime('2015-05-21', 'yyyy-MM-DD')</code><br><br><strong>Hour format should be specified correctly in parse/format date-time functions</strong><br><code>parseDateTime('13:37', 'hh:mm')</code><br><br><strong>MM and mm tokens should be used correctly in parse/format date-time functions</strong><br><code>parseDateTime('2015-05-21', 'yyyy-mm-dd')</code></p><p><code>parseDateTime('13:37', 'HH:MM')</code><br><br><strong>Seconds token should be specified correctly in parse/format date-time functions</strong><br><code>parseDateTime('13:37:01', 'HH:mm:SS')</code><br><br><strong>Week year should not be used in date formatting or parsing</strong><br><code>parseDateTime($Var, 'YYYY')</code><br><br><strong>AM/PM indicator should only be used in combination with lowercase “h”</strong><br><code>formatDateTime($DateTime, 'H:mm a')</code><br></p></td></tr></tbody></table>