Don't say:
Ian's been ill from last Friday.

Say:
Ian's been ill since iast Friday.

Note:
From can also denote a point in time, but it must be followed by to or till: He works from eight o'clock till one o'clock without a break. Place the preposition since before words or phrases denoting a point in time since Monday, since yesterday, since eight o'clock, since Christmas. When we use since, the verb is usually in the ptesent perfect tense, but it may be m the past perfect: I was glad to see Tom. I hadn't seen him since last Christmas.