Adding datetime stamp to JPGs in specific format

[Ludwig]

I'm new to Bulk Rename Utility.

I want to add the jpg photo's datetime taken to the front of the filename (followed by a space then the original filename e.g. DSCnnnnnn IMG_nnnn). I have found how to do this in two steps, but I was hoping it could be done in one. The format I want is YYYYMMDD_HHMMSS e.g. as mobile phones name their photo files. However this option is not available in the format picklist and I cannot figure how to do it under Custom. Any attempt to set a custom format e.g. YMD_HMS ends up as the text that is added as the prefix(!).

What I can do is -
1. add the datetime taken (original) as a prefix (without any underscore using preset 'YMD HMS' format). I tried inserting the underscore at character 9 but that does it at position 9 within the original name, not the "Autodate" modified version.
2. I then need to do a second pass to insert the underscore at character 9.

Not onerous but would be nice to know how to do it in one pass.

[Luuk]

With AutoDate(8) having Format==Custom, the Custom-String can be like... %Y%m%d_%H%M%S

[Ludwig]

With AutoDate(8) having Format==Custom, the Custom-String can be like... %Y%m%d_%H%M%S

Thanks! I didn't realise I had to use %'s in front of the letters .. I saw the "Fmt" picklist with just letters so tried doing the same to get the one I wanted but it didn't work.