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Better dates and times in Python — timezone-aware by default, human-friendly API, and natural language parsing.
2KB immutable date time library alternative to Moment.js with the same modern API
| Metric | arrow | dayjs |
|---|---|---|
| Ecosystem | Python | npm |
| Difficulty | Beginner ✓ | Intermediate |
| Weekly downloads | 2.5M | 43.9M↑ |
| Latest version | v1.3.0 | v1.11.20 |
| Recipes | 1 | 1 |
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Any application dealing with dates across timezones, relative time displays ('posted 2 days ago'), date parsing from strings, date range iteration, or when you want less boilerplate than stdlib datetime.
Use Day.js when you need date parsing, formatting, arithmetic (add/subtract days/months), or comparisons in browser code where bundle size matters. Its plugin system covers timezones, relative time ('3 hours ago'), duration, and ISO weeks.
High-frequency numerical date computations (use numpy datetime64 or pandas Timestamp which are faster). Arrow adds overhead per operation.
For complex timezone-aware calendar applications, consider Temporal (the upcoming TC39 proposal) or date-fns with explicit timezone handling. Day.js's plugin system can grow large if you need many features.
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