Since efdb98eb55e5 cancel move is posted of the cancelled move is already
posted. So the cancelling move can no more be deleted, instead it must be
cancelled without reversal to have the same effect.
The fiscal years are created centered on the passed date such that if the
current day change during the execution, the fiscal year is still usable.
Also fiscal year can be created for a range of dates such that it is guarantee
that the dates are in the fiscal year.
And finally remove datetime and dateutil import when they are not used.
Closes#9977
Cédric Krier