### Theory:

Time is specified in two ways.

1. Ordinary time or $$12$$-Hour format

2. Railway time or $$24$$-Hour format
Ordinary Time or the 12-Hour Format:
• A day has $$24$$ hours. It is divided into two periods; each has $$12$$ hours.

• $$12\!:\!00$$ at night is called midnight, and $$12\!:\!00$$ at day is called noon.

• The $$12$$ hour clock has Ante Meridien (a.m.) and Post Meridien (p.m.).

• Ante Meridien $$-$$ Midnight $$12\!:\!00$$ to Noon $$12\!:\!00$$

• Post Meridien $$-$$ Noon $$12\!:\!00$$ to Midnight $$12\!:\!00$$

Example:
1. $$9\!:\!00$$ a.m. means $$9$$'O clock in the morning (before noon).

2. $$9\!:\!00$$ p.m. means $$9$$'O clock in the night (after noon).
Railway time or $$24$$-Hour format:
• $$24$$-hour clock mostly followed in railways, airways and defence.

• It is the clock from $$0$$ hours to $$24$$ hours.

• $$24$$-hour time format usually has $$4$$ digits. First, two digits are hours, and the last two digits are minutes.

• We don't need to mention morning, noon, evening and night in the $$24$$-hour clock.

• $$12$$ at midnight is denoted as $$00\!:\!00$$ hours.
Example:
1. $$2\!:\!00$$ in the after noon $$=$$ $$14\!:\!00$$ hours

2. $$6\!:\!00$$ in the evening $$=$$ $$18\!:\!00$$ hours
$$12$$-Hour format and $$24$$-Hour format: