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Preposition before noun

How to use “on schedule” correctly

“On schedule” is the standard expression for something happening at the planned time. “Of schedule” is not idiomatic in this meaning.

Quick answer

Which phrase is correct?

Use “on schedule” when something follows the planned timetable. Use “ahead of schedule” or “behind schedule” for timing changes. “Of schedule” is not standard English in this context.

The project is on schedule despite delays.
The train arrived ahead of schedule.
Construction is running behind schedule this month.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
on schedule

Describing planned timing

Use “on schedule” when work or events happen as planned.

The repairs remain on schedule for completion in June.
2
ahead of schedule

Describing early progress

Use “ahead of schedule” when something happens earlier than planned.

The software launch is ahead of schedule.
3
behind schedule

Describing delays

Use “behind schedule” when progress is slower than planned.

The building project fell behind schedule after heavy rain.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
on schedule
The meeting started on schedule.
at the planned time
ahead of schedule
The team finished ahead of schedule.
earlier than planned
behind schedule
Production is behind schedule.
later or slower than planned
of schedule
This expression is not standard for timing.
generally avoided in modern English

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using “of schedule” for timing

English uses “on,” “ahead of,” or “behind,” not “of schedule.”

✕ The flight is of schedule. ✓ The flight is on schedule.

Confusing “on time” and “on schedule”

“On time” is broader, while “on schedule” relates to a planned timetable.

✕ The long-term project is on time. ✓ The long-term project is on schedule.

Leaving out “of” after “ahead” or “behind”

These expressions require “of.”

✕ We are ahead schedule. ✓ We are ahead of schedule.

Quick practice

Choose the expression that matches the intended meaning.

1. The conference started ___ schedule.
2. The team finished two weeks ahead ___ schedule.
3. Due to weather, the project is behind ___.

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Frequently asked questions

Is “of schedule” ever correct?

Not in the meaning of planned timing. Standard English uses “on schedule” or related expressions.

What is the difference between “on schedule” and “on time”?

“On schedule” follows a timetable or plan, while “on time” simply means not late.

Can a person be “on schedule”?

Yes. You can say someone is on schedule with work, training, or goals.

of, about, against, to or for racism? of, about, for, in or on friendship? of, about, for, on or to thing? of, about, for, to or with sex? of, about, on, to or for moon? "of access" or "with access"? "of accommodation" or "for accommodation"? "of accuracy" or "for accuracy"? "of action" or "in action"? "of actor", "with actor" or "by actor"? "of address" or "to address"? "of administration" or "in administration"?

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