Editing Project:Village pump (technical) (section)

== How can a template calculate the diff between year-and-month dates? ==

I'd like a citation template to calculate how old a publication is, because if it's > 3yrs, <code>doi-access</code> should be set to 'free'. Publication is quarterly, and the publisher's dates in their DB are YYYY/MM, so it would be nice if the notice for free access turned on the month. But I can't just subtract the <code>date</code> param from a truncated CURRENTTIMESTAMP, because neither is decimal. I assume this has been done before, just don't know where to look. [[User:Kwamikagami|— kwami]] ([[User talk:Kwamikagami|talk]]) 23:37, 9 August 2022 (UTC)
:You could probably do the calculation using [[Julian day]]s. Or, something like the following usage of {{tl|time interval}} might help. <code>show=d</code> gives a number of days and <code>disp=raw</code> gives just the number. You could use <code>show=y</code> for years but I would need a fair bit of time to experiment or recall how it rounds.
:*<code><nowiki>{{time interval|1 Jan 2001|March 4, 2002|disp=raw|show=d}}</nowiki></code> → {{time interval|1 Jan 2001|March 4, 2002|disp=raw|show=d}}
:[[User:Johnuniq|Johnuniq]] ([[User talk:Johnuniq|talk]]) 00:00, 10 August 2022 (UTC)
::Thanks! I think I can take it from there. If I get stuck I'll ping you. [[User:Kwamikagami|— kwami]] ([[User talk:Kwamikagami|talk]]) 01:13, 10 August 2022 (UTC)
That works! If I plug in 2019-08, it displays as free access; if 2019-09, it doesn't. [[User:Kwamikagami|— kwami]] ([[User talk:Kwamikagami|talk]]) 01:27, 10 August 2022 (UTC)
:{{ping|Kwamikagami}} I had a look at [[Template:Cite JIPA]]. The date/age modules are complex and not fully documented and I have forgotten exactly what <code>partial=on</code> does as far as date differences go, so I'll just mention that using <code>partial=on</code> makes {{tl|time interval}} accept incomplete dates such as "2001" or "March 2001". In a quick test, I couldn't make sense of the resulting number and I can't take the time at the moment to dive in deeper. Ask me in a couple of weeks if you want that investigated (I should do it!). However, what I am confident about is that omitting a date means the current date is used. For example, these give the same result and this may be of use:
:*<code><nowiki>{{time interval|2020-8-10|{{date}}|disp=raw|show=d}}</nowiki></code> → {{time interval|2020-8-10|{{date}}|disp=raw|show=d}}
:*<code><nowiki>{{time interval|2020-8-10||disp=raw|show=d}}</nowiki></code> → {{time interval|2020-8-10||disp=raw|show=d}}
:[[User:Johnuniq|Johnuniq]] ([[User talk:Johnuniq|talk]]) 07:32, 10 August 2022 (UTC)
::Thanks! That simplifies things quite a bit. I'll play around with it tomorrow. [[User:Kwamikagami|— kwami]] ([[User talk:Kwamikagami|talk]]) 08:12, 10 August 2022 (UTC)
:::That allowed me to cut a fair amount of clutter in the code and end up being more forgiving of date formats. Enough that I could reduce the documentation. [[User:Kwamikagami|— kwami]] ([[User talk:Kwamikagami|talk]]) 09:23, 10 August 2022 (UTC)