Since vs For: How to Talk About Time in Work Emails

"I work at this company since 2021." "We are waiting your reply since two weeks." Sentences like these are understandable, but they mark the writer as a non-native speaker right away. Two separate choices are involved: since or for, and which verb tense goes with them. Fix both and time expressions stop being a problem.

1. Since or for: point vs period

The Cambridge Dictionary gives the core rule:

• Use for with a period of time, in the past, present, or future.
• Use since with a point in time in the past.

A quick check: if you can count it (two weeks, three hours), use for. If it names a moment on the calendar or clock, use since.

Cambridge specifically warns that we do not use since with periods of time: "She's been on the phone for hours," not "since hours."

2. For works in any time frame

Cambridge's examples show for in all three time frames:

• Finished past: "He lived in Oxford for 3 years and then he moved."
• Up to now: "They've lived in Oxford for a couple of months."
• Future: "We're going to stay in Oxford for three days."

Since, on the other hand, always looks back from now (or from another reference point) to a starting moment: "They've lived in Oxford since 2004."

3. The tense: present perfect for "up to now"

This is the second half of the mistake. It is tempting to use the present tense for an action that started in the past and continues now, but English uses the present perfect (have/has + past participle) or the present perfect continuous instead.

Cambridge lists this as a typical error: we don't use the present simple or present continuous when we talk about time up to now. Its example:

• Correct: "They've known each other since January."
• Not: "They know each other since January."
• Not: "They're knowing each other since January."

So for anything that started in the past and is still true:

The last example matters. "The server is down for two hours" can sound like a plan for the future, as in a scheduled two-hour outage. "The server has been down for two hours" means it went down two hours ago and is still down. The tense changes the meaning.

4. From...to for start and end points

When something started and ended, Cambridge says to use from, not since:

• Correct: "He worked for that company from 2012 to 2018."
• Not: "He worked for that company since 2012 to 2018."

This shows up constantly in résumés, bios, and project histories. Use the simple past with from...to for finished periods, or for plus the length: "He worked for that company for six years."

5. Choosing the right pattern

6. Before and after

Before: I work in the finance team since 2020. After: I have worked in the finance team since 2020. Why: Started in the past and still true, so present perfect.

Before: We are waiting your confirmation since two weeks. After: We have been waiting for your confirmation for two weeks. Why: "Two weeks" is a period, so for; still waiting, so present perfect continuous. Note "waiting for."

Before: She was our project lead since 2019 to 2023. After: She was our project lead from 2019 to 2023. Why: Start and end points take from...to.

Before: I know Mr. Park since our first meeting in Busan. After: I have known Mr. Park since our first meeting in Busan. Why: Ongoing relationship, so present perfect.

Before: The issue exists since the last update. After: The issue has existed since the last update. Why: "Since the last update" is a point, and the issue continues now.

7. Key takeaways

• Use for with a length of time and since with a starting point in the past.
• Never use since with a period: "for hours," not "since hours."
• For something that started in the past and is still true, use the present perfect, not the present simple.
• Use from...to when you give both a start and an end point.
• The tense can change the meaning: "has been down for two hours" is not the same as "is down for two hours."