Different Ways to Illustrate Past Event in Calendar

Question

I am making an interactive calendar, where user can make an event for themselves, or to invite others (very much similar to Google Calendar).

Only difference from G Cal is that these events has a state of "completion". Completion is happening automatically, and there is nothing user needs to take an action. However, the system that updates the calendar:
a) only updates once couple hours
b) sometimes the performance fails

So I need to indicate that the event did not perform one way or the other (there is no way to be able to distinguish why until someone manually looks at it.

So far, my ideas were:
1. Do it like google (past event is in pale color. if the event did not performed yet/ failed, show it as a future event in full color)
2. Do strikethrough style (line in the middle) for the past event.
3. Put some sort of 'error' or 'pending' icon next to event title.

Solution 2 is, I looked up strikethrough, but grammatically that's a scramble, rather than a meaning of completion, so I am hesitant to use it.

Solution 3, the challenge is the calendar is already full of information and already very hard to digest what's going on. I am not interested in adding another icon that user needs to learn and be familiarize themselves.

I am wondering if there is any other method to indicate this special indication.

Answer 1

You've mentioned your calendar is similar to Google Calendar, it is worth to be consistent with it. You have three event states which are future, pending (unconfirmed) and past.

As future and past events are color-coded in Google Calendar, to be consistent, use same mean for pending events. It could be yellowish (middle transition state, like traffic-light) or orange toned (current event).

It is also necessary for users to understand the essence of the events' states. It could be achieved with system description, FAQ section, tooltip for calendar events.