In or On the Second Week? How to Choose the Right Preposition
When you’re drafting an email, a report, or even a casual text, the choice between in and on before “the second week” can feel oddly decisive. It’s one of those tiny grammar puzzles that, if mishandled, makes a sentence sound off to native ears. Below we’ll untangle the rule, spot the exceptions, and give you concrete examples so you can write with confidence the next time the calendar flips to week two.
Why Prepositions Matter with Time Expressions
Prepositions are the invisible glue that connects time words to the rest of a sentence. Using the wrong one doesn’t usually break the grammar, but it does change the nuance. “In” suggests a period within which something happens, while “on” pins an event to a specific day or date. That distinction becomes crucial when weeks are involved because a week is both a span of days and, sometimes, a reference point for a single day.
The General Rule: Use “In” with Weeks
When you refer to an entire week as a block of time, the preposition in is the go‑to choice. Think of the week as a container—something occurs in that container.
- Correct: The training program starts in the second week of July.
- Correct: We expect the results in the second week after launch.
- Correct: She will travel in the second week of her sabbatical.
In each case, the action is understood to happen at some point during the seven‑day stretch, not on a particular calendar day.
When “On” Can Slip In
“On” enters the picture when the week is being treated like a specific date rather than a span. This usually happens in two scenarios:
1. When a day of the week is named
If you specify a day, the preposition switches to on. The week becomes a reference point for that day.
- We’ll meet on Monday of the second week.
- The deadline is on Friday in the second week of the quarter.
2. In idiomatic or informal speech
Some speakers blur the rule for brevity, saying “on the second week” when they really mean “in the second week.” While many listeners understand the intent, it’s considered nonstandard in formal writing.
Common Mistakes and How to Fix Them
Even seasoned writers slip up. Here are a few frequent errors and quick fixes:
- Mistake: The survey will close on the second week of May.
Fix: The survey will close in the second week of May. - Mistake: I’ll start the project on the second week.
Fix: I’ll start the project in the second week. - Mistake: She arrived on the second week of her stay.
Fix: She arrived in the second week of her stay.
Notice the pattern: replace “on” with “in” unless a specific weekday follows.
Quick Checklist Before You Hit Send
Use this short list as a mental safety net:
- Is the reference a whole week? → Choose in.
- Are you naming a day (Monday, Tuesday, etc.) within that week? → Choose on.
- Is the context informal and the audience likely to overlook the slip? → You may get away with “on,” but in is still safer.
Examples Across Different Contexts
Seeing the rule in action helps cement it. Below are snippets from business, education, and everyday life.
Business
Our quarterly review is scheduled in the second week of October, and the final report will be distributed on Thursday of that week.
Education
Students will receive feedback in the second week after the assignment is submitted.
Everyday Conversation
We’re planning a road trip in the second week of August; let’s decide the exact day on Monday.
FAQ
Can “during” replace “in” for weeks?
Yes, “during” works when you want to emphasize that something occurs throughout the week, e.g., “During the second week of the conference, we’ll host several workshops.”
Is “at” ever correct with weeks?
“At” is not used with weeks. It pairs with specific clock times (e.g., “at 3 p.m.”) or precise moments (“at the start of the week”).
What about “by the second week”?
“By” indicates a deadline before the end of that week, so “by the second week of May” means any time up to the close of that week.
Does British English differ?
The preposition rule is the same in both British and American English. The main variation lies in spelling and some idiomatic phrasing, not in “in” vs. “on” usage.
