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# Why the replace function is not accepted by this question?

I was working on the challenge for datetime.timedelta and the question didn't like my following solution for the years:

```date == 'years':
return starter.replace(starter.year + num)
```

I know I could do this

```date == 'years':
return starter + datetime.timedelta(days = num * 365)
```

I get the same result from both line of code for a simple tests. Could you please let me know why the replace function was not accepted? Thank you!

It would help to see the entire solution that was submitted to the challenge.

Aha, I see now. The trick is in the expedience suggested by the comments: "Consider a year to be 365 days."

Your approach is actually better, because when there is an intervening leap year, the results in the suggested method will be slightly off. But the challenge is expecting those values.

Hello Steven, Please find the function below:

import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29) def time_machine(num, date): if date == 'minutes': return starter + datetime.timedelta(minutes = num) elif date == 'hours': return starter + datetime.timedelta(hours = num) elif date == 'days': return starter + datetime.timedelta(days = num) elif date == 'years': return starter.replace(starter.year + num)

Examples from running the function:

time_machine(5, "minutes") datetime.datetime(2015, 10, 21, 16, 34)

time_machine(5, "years") datetime.datetime(2020, 10, 21, 16, 29)

To preserve the integrity of posted code, use the instructions for code formatting in the Markdown Cheatsheet pop-up below the "Add an Answer" area.   Or watch this video on code formatting.

Thank you so much Steven!