While we're kept occupied by some tasks, we may have lose the attention of the time, and may miss certain important events.

But with using Mac, you can set the clock to auto-announce the time every hour. Setting can be made easily with these steps:

1. Go to your menubar and there you should be able to find your clock displayed
2. Click it and choose Open Date & Time…
3. Go under Clock section
4. Tick the checkbox: Announce the Time

Not only set it to announce every hour, but there is also options for you to set the announcement to be made at interval of half hour or even quarter hour.

Obviously, don't try this in your office with your volume turned to maximum. You will annoy your colleagues, especially if you're using Hysterical as your custom voice.