I've got a template for a store and I use repeater for opening hours.
When I'm on the store page I would like to search inside this repeater to find the hours related to a precise day.
Is it possible with selectors?
Just some explanation because it is interesting...
This isn't something that is specific to Repeaters - it applies to any selector used on a PageArray/WireArray (a Repeater field returns a PageArray).
When you do $some_pagearray->find() this is different to a $pages->find() - the method name is the same but they are actually totally different methods. See find() method in the PageFinder class vs the WireArray class.
When using $pages->find() the method refers back to the fieldtype for each queried field and the fieldtypes can do some special preparation to the queried value. In the case of a Datetime field the value is passed through strtotime() if it is a string. So this allows "today" to be converted to a timestamp.
But when using $some_pagearray->find() this process does not happen, so the queried value must be a timestamp.
Another gotcha to watch out for is using the page status as a string in a selector. With $pages->find() you can do something like "status!=hidden" but this won't work with a selector in $some_pagearray->find().
I think it would be nice if things like this did work with PageArrays - there is an open request for it.