VALARM Description Is Not Showing

VALARM Description Is Not Showing

I am trying to create a valarm for a vevent with customized vlarm message.
So based on RFC5545, I just have to set action to DISPLAY and set my
customized message in the DESCRIPTION field of the VALARM component.
"When the action is "DISPLAY", the alarm MUST also include a "DESCRIPTION"
property, which contains the text to be displayed when the alarm is
triggered."
However, even if I set the DESCRIPTION property, the message is still not
being displayed in the alarm popup.
BEGIN:VALARM
ACTION:DISPLAY
TRIGGER;VALUE=DURATION:-PT15M
DESCRIPTION:Test Message
END:VALARM
I have tried it on my iphone calendar application and Mozilla Thunderbird
Lightning Addon.
Any feedback is greatly appreaciated.
Thank You.