What is time tag in HTML5 and how to use it?

The time tag in HTML5 is used to represent a specific period in time. This could be a date, a time, or a duration. The tag is useful because it provides a machine-readable way to specify a time, which can be used by browsers, search engines, and other web technologies for a variety of purposes.

The tag typically uses the “datetime” attribute, which provides the specific time in a standard format.

Example:

```
May 7, 2022
```

In the example above, we represent the date May 7, 2022. This date is both human readable (as the text between the opening and closing time tags), and machine readable (as the value of the datetime attribute).

You can also represent time:

```
1:00 PM
```

In the example above, we represent the time 1:00 PM. Again, the time is both human readable and machine readable.

You can also represent date and time together:

```
1 PM on May 7, 2022
```

In this example, we’re representing both the date and time.

Finally, you can represent durations:

```
Two and a half hours
```

This example represents a duration of two and a half hours. Durations use the ISO 8601 duration format.