Time and Temperature - 24-hour Clock and 12-hour Clock

The 12-hour clock system divides a 24-hour day into two periods: a.m. (Ante Meridiem, meaning before noon) and p.m. (Post Meridiem, meaning after noon). Visually, a standard analog clock face shows numbers 1 to 12, and the hour hand completes two full circles to represent one full day.

The 24-hour clock system, often used by railways and airlines, expresses time as a continuous scale from 00:00 to 24:00. This system eliminates the need for a.m. and p.m. notation. Visually, this can be imagined as a long horizontal timeline where the hours progress from 00, 01, 02... up to 23 and then reset at midnight.

To convert 12-hour a.m. time to 24-hour format: For times between 1:00 a.m. and 11:59 a.m., the numbers remain the same but are written as four digits (e.g., 08:30 hours). For the first hour of the day (12:00 a.m. to 12:59 a.m.), we replace 12 with 00 (e.g., 12:15 a.m. becomes 00:15 hours).

To convert 12-hour p.m. time to 24-hour format: For 12:00 noon, it remains 12:00 hours. For times from 1:00 p.m. to 11:59 p.m., add 12 to the number of hours and remove the 'p.m.' label (e.g., 2:00 p.m. becomes $2 + 12 = 14:00$ hours).

To convert 24-hour time back to 12-hour time: If the hours are less than 12, it is a.m. (except 00 which becomes 12 a.m.). If the hours are exactly 12, it is 12 p.m. (noon). If the hours are greater than 12, subtract 12 from the hours and add the 'p.m.' label (e.g., 17:00 hours becomes $17 - 12 = 5:00$ p.m.).

Calculating time duration (elapsed time) involves finding the difference between the end time and the start time. When subtracting time, if the minutes in the start time are greater than the minutes in the end time, borrow 1 hour and convert it to 60 minutes. Visually, this is similar to vertical subtraction used in standard arithmetic but using a base of 60 for minutes.

Temperature is the measure of hotness or coldness of an object, measured using a thermometer. The two most common scales are Celsius ($^\circ C$) and Fahrenheit ($^\circ F$). On a visual thermometer scale, $0^\circ C$ corresponds to $32^\circ F$ (freezing point of water) and $100^\circ C$ corresponds to $212^\circ F$ (boiling point of water).