In Verbs^x, Indirect speech^x, Adverbs^x

Hi all, Please fix my mistakes. Adverbs and adverbial phrases of time change as follows: 1/Direct: Yesterday, a day ago, one day ago. Indirect: The day before, the previous day, a day before, a previous day. (That means the indirect forms of "yesterday" , " a day ago" , "one day ago" are...

I'm merely an English learner and I don't know much about English. However, I think English speakers often use a construction "X (=a period or time span) before" to mean a sense almost similar to "X ago". This kind of construction seems to be often used in an indirect speech. (Direct speech)...