There is no specific time. You will be able to tell when the moment is right, i would think after a date or two it's okay to call her that. :) depends on the person really.
You can call HONEY, SWEETHEART, BABY, DARLING etc...
Something that you call a loved one, such as "sweetheart," "darling," "my love," etc.
honey, darling, sweetheart, dear, etc
sweetheart, my love, darling... you can also call him boo, sugar, pumpkin, baby boy, ect
Let Me Call You Sweetheart was created in 1910.
Sweetheart
Vugglemantis
you can call them, Honey, dear, lovey, or even buddy
The cast of Let Me Call You Sweetheart - 1932 includes: Ethel Merman as herself
Those are nicknames that yo call your Boyfriend or Girlfriend. Like I do, Sweetheart.
Let Me Call You Sweetheart - 1997 TV is rated/received certificates of: Australia:PG UK:12
He called her "querida." According to the Spanish-English dictionary this is translated as Darling or Sweetheart. More literally, it means "she whom I desire."