**Understanding Hours and Time Formats**

**What is an Hour?**
An hour is a unit of time equal to 60 minutes, with each minute consisting of 60 seconds. There are 24 hours in a complete day.

**Time Format Systems**

**12-Hour Clock:**
– Uses numbers 1-12
– AM (ante meridiem): Before noon (midnight to noon)
– PM (post meridiem): After noon (noon to midnight)
– 12 AM = midnight | 12 PM = noon
– “12 midnight” and “12 noon” help avoid confusion

**24-Hour Clock:**
– Uses numbers 00-23
– 00:00 = midnight | 23:59 = last minute before midnight
– Runs from midnight to midnight continuously
– Also called “military time” in some countries
– Eliminates AM/PM ambiguity

**Hours in Different Time Periods**

| Time Period | Hours |
|————-|——–|
| Day | 24 |
| Week | 168 |
| Month | 672 (28-day month) |
| | 696 (29-day month) |
| | 720 (30-day month) |
| | 744 (31-day month) |
| | 730.5 (average) |
| Year | 8,760 (365-day year) |
| | 8,784 (366-day leap year) |
| | 8,766 (average) |
| Decade | 87,648 (2 leap years) |
| | 87,672 (3 leap years) |
| | 87,660 (average) |
| Century | 876,600 |