there's not a built-in function that can convert to Julian dates in Denodo.
These are the date pattern currently available in Denodo Platform: [Date and Time Pattern Strings](https://community.denodo.com/docs/html/browse/8.0/vdp/vql/appendix/date_and_time_pattern_strings/date_and_time_pattern_strings#java-date-and-time-patterns-used-in-virtual-dataport).
If you're working with JDBC/ODBC Data Source and your database has already a built-in or a custom functions to convert in Julian day you can take advantage of it by delegating the conversion to the Data Source. You just have to create the base view in VDP with the *Create from Query* option [Creating Base Views from SQL Queries](https://community.denodo.com/docs/html/browse/8.0/en/vdp/administration/creating_data_sources_and_base_views/jdbc_sources/jdbc_sources#creating-base-views-from-sql-queries).
In alternative you can make the conversion using [DateTime](https://community.denodo.com/docs/html/browse/8.0/en/vdp/vql/functions/datetime_functions/datetime_functions#datetime-functions) and [Text](https://community.denodo.com/docs/html/browse/8.0/en/vdp/vql/functions/text_functions/text_functions#text-functions) functions but the formula for the conversion that I'm finding on internet are a little bit complex and I would suggest to create a custom function using Java which can be added to VDP as a Jar extension. Have a look at [Developing Custom Functions](https://community.denodo.com/docs/html/browse/8.0/en/vdp/developer/developing_extensions/developing_custom_functions/developing_custom_functions).
Hope this helps