present:i can . et au passé:i could ?
1. talking about general ability in the past:
I can cycle. [present]
I could cycle when I was ten. [past]
2. in reported/indirect speech:
She says her parrot can talk. [direct speech]
She said her parrot could talk. [reported speech]
Brian: I had two pens.
Clearly this is a past tense/past time situation which tells us that Brian no longer has the two pens.
Brian: I have two pens.
Joan: What did Brian say, Tanya?
Tanya: He said that he had two pens.
In Tanya's sentence, the 'had' is only a FORM of the past tense. It doesn't actually describe any past tense, does it? We understand that despite the past tense FORM, Brian has two pens.
In modern English, modal verbs are tenseless auxiliary verbs.
Referring back to the examples I gave - according to some grammars and dictionaries like Oxford or Cambridge, could is still regarded as the past tense form of can. Obviously, could can't be used in every case referring to past abilities of present abilities that are described by can.