**How to calculate time?**

Calculating time involves determining the duration or the interval between two specific points in time. It can be done using various methods, including manual calculations or by using digital tools such as calculators or mobile apps.

**Manual Calculation:**

To calculate time manually, you need to consider the following factors:

1. **Units of Time:** Time can be measured in different units, such as seconds, minutes, hours, days, weeks, months, or years. It is crucial to ensure that both the starting and ending points are expressed in the same unit of time.

2. **Time Difference:** Determine the time difference between the starting and ending points. For example, if you want to calculate the time between 9:00 AM and 11:30 AM, the time difference is 2 hours and 30 minutes.

3. **Conversion:** If the time difference is expressed in different units, convert it to a common unit. For instance, if the time difference is given as 2 hours and 30 minutes, convert the minutes to hours (30 minutes = 0.5 hours) and add it to the existing hours.

4. **Addition or Subtraction:** Depending on the scenario, you may need to add or subtract the time difference from a given starting point. For example, if you want to calculate the time after 2 hours and 30 minutes from 9:00 AM, you would add the time difference to the starting time.

**Digital Tools:**

In addition to manual calculations, digital tools can simplify time calculations. Many calculators, mobile apps, and online platforms have built-in time conversion and calculation features. These tools allow you to input the starting and ending times and provide the calculated duration automatically.

**Conclusion:**

Calculating time involves determining the duration between two specific points. It can be done manually by considering the units of time, time difference, conversion, and addition or subtraction. Alternatively, digital tools such as calculators or mobile apps can simplify the process.

1. Work out the longitude difference.
2. Convert this to a time difference.
3. Adjust the time according to the direction of movement (east or west).
Example. What is the time in Calcutta (longitude 96 degrees east) when it is 9.00 a.m. in Munich (longitude 11 degrees east)?
1. Longitude difference = 85 degrees
2. Time difference 85/15 = 5 hours 40 minutes
3. Calcutta is east of Munich, therefore the time is ahead.
Thus 9.00 a.m. plus 5 hours and 40 minutes = 2.40 p.m...