# regex - where and how?

**URL:** <https://community.mp3tag.de/t/regex-where-and-how/9708>\
**Category:** Support\
**Created:** [January 15, 2010, 12:57pm UTC](https://community.mp3tag.de/t/regex-where-and-how/9708 "2010-01-15T12:57:40Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![tillebeck](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/t/9de0a6/32.png) [@tillebeck](https://community.mp3tag.de/u/tillebeck)\
**Post date:** [January 15, 2010, 12:57pm UTC](https://community.mp3tag.de/t/regex-where-and-how/9708/1 "2010-01-15T12:57:40Z")

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Hello

Just installed the MP3Tag after recommandation from a forum post I did in another forum.

I have a "simple" task but cannot seem to crack the nut and get started with this popular tool

I need to change many filenames:

File names are: ddmmyyyy.xls (e.g. 15012010 for 15th Jan 2010)  
and I would like: yyyymmdd.xls (e.g. 20100115.xls)

How to do this?

1. add xls to allowed file types (done)
2. find nice regex to alter filename: /^(\d{2})(\d{2})(\d{4}).xls$/i
3. somehow get the Mp3Tag to change filenames from ddmmyyyy.xls to yyyymmdd.xls

Obviously it is #3 that I really would like a quided tour through.

BR. Anders

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**Author:** ![dano](https://community.mp3tag.de/user_avatar/community.mp3tag.de/dano/32/6_2.png) [@dano](https://community.mp3tag.de/u/dano)\
**Post date:** [January 15, 2010, 2:44pm UTC](https://community.mp3tag.de/t/regex-where-and-how/9708/2 "2010-01-15T14:44:36Z")

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Before you go any further, have you successfully loaded a xls file in Mp3tag?  
Adding an arbitrary extension to the options does not make Mp3tag able to work with this extension.

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**Author:** ![tillebeck](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/t/9de0a6/32.png) [@tillebeck](https://community.mp3tag.de/u/tillebeck)\
**Post date:** [January 15, 2010, 5:45pm UTC](https://community.mp3tag.de/t/regex-where-and-how/9708/3 "2010-01-15T17:45:07Z")

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Ok, thanks. I will look more into the documentation. I am able to choose convert filename-\>filename and type ind the rules regex to {1}{2} etc. but can only press cancel since the "go" and "Example" buttons are greyed out.

Br. Anders

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**Author:** ![dano](https://community.mp3tag.de/user_avatar/community.mp3tag.de/dano/32/6_2.png) [@dano](https://community.mp3tag.de/u/dano)\
**Post date:** [January 15, 2010, 6:07pm UTC](https://community.mp3tag.de/t/regex-where-and-how/9708/4 "2010-01-15T18:07:23Z")

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Ok it seems it is possible to add a custom extension.

Regex is availale from actions:  
[/t/967/1](https://community.mp3tag.de/t/967/1)

But also works in Convert with $regexp() function

For Convert \> filename - filename:

old mask:  
%1  
new mask:  
$regexp(%1,^(\d{2})(\d{2})(\d{4})$,$3$2$1)

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<div class="post-metadata">

**Author:** ![tillebeck](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/t/9de0a6/32.png) [@tillebeck](https://community.mp3tag.de/u/tillebeck)\
**Post date:** [January 18, 2010, 9:55am UTC](https://community.mp3tag.de/t/regex-where-and-how/9708/5 "2010-01-18T09:55:32Z")

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Thanks

I couldn't quite figure it out. Mainly because of a simple basic error:  
it is not enough to list files in the windows. One also have to mark/highlight/choose them.

When that was done I could click the "Convert - Quick" and choose "With Regex"

and did:  
field: \_FILENAME  
from: ([0-9]{2})([0-9]{2})([0-9]{4})  
to: $3-$2-$1

All files named ddmmyyyy.xls are now yyyy-mm-dd.xls

Thank for the help  
Anders

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<div class="post-metadata">

**Author:** ![system](https://community.mp3tag.de/uploads/default/original/2X/c/ce7035d426cb755a7916793326d23b465222a407.png) [@system](https://community.mp3tag.de/u/system)\
**Post date:** [February 9, 2026, 12:22pm UTC](https://community.mp3tag.de/t/regex-where-and-how/9708/6 "2026-02-09T12:22:06Z")

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