⏳ Grammar · Past & Perfect Tenses
For, Since & Ago
Three small time words that decide the whole sentence around them — learn where each one belongs and the mistakes disappear.
Grammar › Past & Perfect Tenses › For, Since & Ago
The rule in one sentenceUse for with a length of time, since with a starting point, and ago to count backwards from now with the past simple.
Three words, three jobs
These three words all talk about time, which is exactly why learners mix them up — but each one answers a different question.
For answers “how long?” and is always followed by a length of time, a duration: Hugh Jackman has played Wolverine for more than a decade. It doesn’t matter when the period started — only how much time it covers.
Since also answers “how long?”, but it names the exact starting point rather than the length: The James Bond franchise has run since 1962. You could always rephrase a “since” sentence with “for” if you calculate the length instead — but “since” gives you the fixed point on the calendar.
Ago is different again: it measures backwards from right now to a finished moment in the past, and it always pairs with the past simple, not the present perfect. Jerry Maguire came out nearly 30 years ago.
🎬 Compare: “Francis Ford Coppola has been making films for over 50 years” (length) vs. “Francis Ford Coppola has been making films since 1969″ (starting point) vs. “Francis Ford Coppola released Apocalypse Now more than 45 years ago” (counting back to one finished event).
Same director, three different tools for talking about time — pick the one that matches what you actually know.
Notice that ago behaves completely differently from the other two: it doesn’t go with “have/has” at all. As soon as you see ago, expect a simple past verb nearby, not a present perfect one.
How to build each one
FOR — a length of time
Pairs naturally with the present perfect, because the period usually continues up to now.
Wild Tales has entertained festival audiences for more than a decade since its 2014 release.
SINCE — a starting point
Also pairs with the present perfect — the fixed point is where the situation began.
Disney has owned Marvel Studios since 2009.
AGO — counting back from now
Always with the past simple, because it names a specific, finished moment.
The Fugitive was released more than 30 years ago.
When to use which
Use for / since when…
- The situation is still true now: Zack Snyder has worked with composer Hans Zimmer for over a decade.
- You want to give a length of time: use for — Keanu Reeves has played John Wick for over a decade.
- You want to name the exact start: use since — The Men in Black series has run since 1997.
Use ago when…
- You’re counting back to one finished point: The first Incredibles film came out more than 20 years ago.
- The event is closed, not continuing: The first Academy Awards ceremony took place over 90 years ago.
- The verb is past simple, not present perfect: Marvel Studios announced Avengers: Doomsday a month ago. (not “has announced”)
Signal words in context
Spotting which word triggers which pattern makes the choice automatic.
Typically follows “for”
Typically follows “since”
Typically follows “ago”
Visual guide
Teacher Teddy’s illustrated guide to this rule is being drawn — the full swipe-through infographic will appear here soon.
Common mistakes
❌ David Fincher has directed films since 30 years.
✅ David Fincher has directed films for 30 years.
“30 years” is a length of time, not a starting point — that needs “for”, not “since”.
❌ I watched Election since a week.
✅ I watched Election a week ago.
A single finished event needs “ago” and the past simple, not “since” with a present perfect.
❌ Pixar has released Inside Out 2 two years ago.
✅ Pixar released Inside Out 2 two years ago.
“Ago” never combines with the present perfect — switch “has released” to the past simple “released”.
British vs American note: Both British and American English follow this rule identically — the for/since/ago pattern doesn’t shift between the two.
Exceptions & tricky cases
Three points that go beyond the basic rule.
1. “For” can also describe a finished period in the past simple. Al Pacino trained as a stage actor for several years before his breakout film role — here “for” gives a length inside a finished past-simple story, not a present-perfect situation.
2. “Since” can start a clause, not just a date. Ever since Boogie Nights became a cultural phenomenon, Paul Thomas Anderson has been one of Hollywood’s most in-demand directors. “Since” plus a full clause still marks a starting point.
3. You can convert between “for” and “ago” with a small calculation. If a franchise “started 20 years ago” and is still running, you can also say it “has run for 20 years” — the facts match, but the grammar (tense and word choice) must change together.
Practice: choose the right word
Eight quick questions. Pick the answer you’d actually say — you get the explanation either way.
1. Harrison Ford has played Indiana Jones ___ over 40 years.
“40 years” is a length of time → for.
2. The Marvel Cinematic Universe has existed ___ 2008.
“2008” is a fixed starting point → since.
3. The first Shrek film came out more than 20 years ___.
Counting back to a single finished release → ago.
4. Denzel Washington ___ Training Day more than two decades ago.
“Ago” always pairs with the past simple, never the present perfect.
5. Scarlett Johansson has starred in Marvel films ___ she joined as Black Widow in 2010.
A whole clause naming the starting event → since.
6. Studio Ghibli has been making animated films ___ more than four decades.
“More than four decades” is a duration, not a fixed date → for.
7. Leonardo DiCaprio won his first Oscar several years ___, for The Revenant.
Counting back from now to a single finished award → ago.
8. Universal Pictures has owned the Despicable Me rights ___ the franchise began in 2010.
“The franchise began in 2010” is the starting point → since.
Keep going
Related lessons in Past & Perfect Tenses:
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