The inclusion of any of the time parameters in a countdown is optional; you can show as many or as few time periods as you want.

If you're using the countdown in an email, it’s rendered as a single image. When someone opens the email, the timer shows the remaining time at that point, but the seconds start at 59 regardless of the actual number of seconds remaining. The seconds tick down to zero, and then start over. None of the other figures change while the email is kept open.

If the recipient re-opens the email at a different time, all of the figures update to show the time remaining, and the seconds again resume ticking down from 59.

Some email clients, notably Gmail, cache images for a period of time—10-20 minutes—and so if the email is re-opened within that window, the timer remains static and doesn’t update. If the recipient opens the email again after the cached time, they see an up-to-date remaining countdown.

Using a Countdown SmartBlock on your website works differently and all periods tick down without a page refresh.