Time Units Guide
From nanoseconds to millennia — understand how we measure time in science, computing, and everyday life
Overview
Time is one of the fundamental dimensions of the universe. We measure time using units ranging from tiny nanoseconds in computing to millennia in history and geology.
The second is the SI base unit of time, defined by the vibration frequency of cesium atoms.
Common Time Units
| Unit | Symbol | In Seconds | Common Use |
|---|---|---|---|
| Nanosecond | ns | 0.000000001 | Computing, electronics |
| Microsecond | μs | 0.000001 | Photography, computing |
| Millisecond | ms | 0.001 | Response time, latency |
| Second | s | 1 | SI base unit |
| Minute | min | 60 | Daily time |
| Hour | h | 3,600 | Daily time, work |
| Day | d | 86,400 | Calendar |
| Week | wk | 604,800 | Calendar |
| Month | mo | ~2,629,746 | Calendar (avg 30.44 days) |
| Year | yr | 31,556,952 | Calendar (365.2425 days) |
Scientific Time Scales
Very Small Time
- Planck time: 5.39 × 10&sup-44; s (smallest meaningful time)
- Attosecond: 10&sup-18; s (electron motion)
- Femtosecond: 10&sup-15; s (molecular vibration)
- Picosecond: 10&sup-12; s (transistor switching)
Very Large Time
- Decade: 10 years
- Century: 100 years
- Millennium: 1,000 years
- Megayear: 1,000,000 years (geology)
- Gigayear: 10&sup9; years (cosmology)
Real-World Time References
Eye Blink 100-400 ms
Heartbeat ~800 ms
Earth Rotation 23h 56m 4s
Lunar Month 29.53 days
Earth Orbit (Year) 365.25 days
Light to Moon 1.28 seconds
Light from Sun 8 min 20 sec
Dinosaur Extinction 66 million years ago
Quick Conversion Tips
Hours ↔ Minutes
1 hour = 60 minutes
Divide minutes by 60 for hours
Days ↔ Hours
1 day = 24 hours
Multiply days by 24 for hours
Years ↔ Days
1 year ≈ 365.25 days
Use 365 for quick estimates
Weeks ↔ Days
1 week = 7 days
1 year ≈ 52 weeks