"modest" use of could for can.

in the present time, and in the "modest" use of could for can. (Could you tell me the right time), of would for will (Would you kindly tell me ... ) and of might for may (Might I ask ... ). It has finally led to the change of must from a preterit into a. present tense; cf. also Swed. maste. Further details must be left. to special grammars.