a week yesterday

a week tomorrow/on Monday/Tuesday/etc.

One week from the day specified. Primarily heard in UK. I'm flying to Ireland a week on Saturday for my brother's wedding. We need that report finished a week tomorrow.
See also: Monday, on, tomorrow, Tuesday, week

a week yesterday

A week and a day before today. I last saw Stu a week yesterday, before he left on vacation.
See also: week, yesterday

a week yesterday/last Monday/Tuesday/etc.

One week before the day specified. They only gave me the assignment a week yesterday, so I'm really stressed out about getting it finished by tomorrow. Chris left on his work trip a week last Tuesday.

a ˌweek ˈyesterday, last ˈMonday, etc.

(especially British English) seven days before the day that you mention: It was a week yesterday that we heard the news.
See also: last, week