I never heard of anyone saying "the" lunch?
When is "lunchtime"?
I never heard of anyone saying "the" lunch?
When is "lunchtime"?
One would refer simply to 'lunchtime', avoiding 'the'.
By it's definition lunchtime refers to noon (the middle of the day, 12:00), but this can vary greatly per social circle.
Examples sentences:
Is it lunchtime already?
Are you coming for lunch as well?