The Date Formats global option changes the default date format for all maps or forms. However, the format of the existing date fields do not change; the default is only used for new maps or forms.
GeoJSON is a geospatial data interchange format based on JavaScript Object Notation (JSON). It defines several types of JSON objects and the manner in which they are combined to represent data about geographic features, their properties, and their spatial extents. GeoJSON uses a geographic coordinate reference system, World Geodetic System 1984, and units of decimal degrees.
OpenDocument Spreadsheet Document Format (ODS), Version 1.2, ISO 26300:2015
Format Description for ODF_spreadsheet_1_2 -- An XML-based, international standard format for a spreadsheet that is editable. Usual file extension is .ods. Documented with formats for other content categories in the OpenDocument Format (ODF) 1.2. Standard developed by OASIS and also approved as ISO/IEC 26300:2015. Supersedes ODS 1.1.