Link to previous day in MediaWiki?

Question

I have a university-managed wiki with the basic templated from MediaWiki, but I have been adding more copying them from the Wikipedia templates.
We use it as a lab book so there is a page per day, e.g. 2018/02/02.

I want to write a link to the previous day, i.e. yesterday, 2018/02/01.

I tried:

{{CURRENTYEAR}}/{{CURRENTMONTH}}/{{#expr:{{CURRENTDAY}}-1}} ,

but this returns 2018/02/1.

• How do I make the day have the 0 before the single digit? As in I want 2018/02/01 and not 2018/02/1.

• My method would only work for days within the same month. Is there a wikipedia template for yesterday? How would I write it for the generic date? With a bunch of If statements to check if the month has changed?

Answer 1

You can use the #time parser function to do some date calculations (anything that's supported by the strtotime() PHP function), for example:

[[{{#time:Y/m/d|now - 1 day}}]]

Or for the day before a particular day:

[[{{#time:Y/m/d|1 April 2017 - 1 day}}]]