Timing Application for Permanent Residence

Hello everybody,  I would really appreciate some help!

I arrived in Spain on 15 November 2016 and applied for Temporary Residence on 5 December 2016.  My temporary residence card (the bit of green paper says desde 5 Dic 2016) lasts up to 5 years.  However, I can only apply for Permanent Residence once I have lived here more than 5 years.  5 December 2021 is a Sunday.  If I go on 3 December 2021 then presumably I'm too early to apply for Permanent Residence; HOWEVER if I go on 7 December (with 6 and 8 being national holidays) then my temporary residence card has already expired (which sounds bad!).

Please can somebody tell me - when do people usually apply for Permanent Residence to get around this problem? Is there a bit of leeway in terms of the dates?

Thanks in advance.

You can renew residency within 60 days before its expiration or 90 days after.

All you need to know:- http://www.exteriores.gob.es/portal/en/serviciosalciudadano/informacionparaextranjeros/paginas/inicio.aspx