Meaning: The counting backwards from a certain number to zero started with a feeling of being very happy and eager.
Choice of Words: Countdown means counting backwards from a certain number to zero. Excitement means feeling very happy and eager.
Alternative Expressions
The timer started with joy.
Meaning: This means that the time leading up to something important started with a lot of happiness.
Choice of Words: The timer is a device that counts down the time until something happens. Started means it began. Joy is a feeling of great happiness.
The waiting period commenced with anticipation.
Meaning: This means that the time leading up to something important started with a lot of excitement and eagerness.
Choice of Words: The waiting period is the time when you have to wait for something to happen. Commenced means it started. Anticipation is a feeling of excitement and eagerness for something to happen.