In the Options menu click on Enable Time Marker. This enables the time marker function if disabled, or disables it if enabled.
Choose Options Enable Time Marker (ALT, O, M). This procedure also enables the time marker function if disabled, or disables it if enabled.
When the time marker function is enabled, a check mark is displayed on the Options menu immediately preceding the Enable Time Marker command. This check mark indicates that the time marker function is enabled, even though it might not be immediately obvious on the screen for various reasons. When the time marker function is disabled, the check mark is not displayed.