Why this only on Android? or is that used for that dummy library?

Feels like this should go into ECM?

org.kde.kirigamiaddons.private.dateandtime to emphasis it's an impl detail

theDate is a bit awkward since that's what you'd have to use when you use the signal

KF5KirigamiAddonsDateAndTime?

Generally conversions between C++ timedate and JavaScript Date is bad. There's no way to represent just a time with no date and timezone associated with it in JavaScript.
While it's ugly, I'd suggest we return a bunch of int.
Also, I think we should have the selected time as properties and an accepted/rejected signal or similar.
(Same probably goes for the date picker)

Use QtObject for this then

Unused

dateMethods

Coding style

Better name please

There's QDateTime::currentMSecsSinceEpoch()

Just forward-declare?

Generally we want singletons to return references these days to communicate ownership properly

const QDate &

You need to set

QQmlEngine::setObjectOwnership(..., QQmlEngine::CppOwnership);

A QObject singleton type instance returned from a singleton type provider is owned by the QML engine unless the object has explicit QQmlEngine::CppOwnership flag set.

It's for the dummy library only

Yep

I'd rather do that in a separate patch since it should also be done for other classes

In this particular case the timezone is not relevant though

If we do this should the date thing also use ints for symmentry?

Actually clazy disagrees, QDate and QTime should be passed by value