The day didn’t have to coordinate with the date.
Jewish tradition records the first manna fell on a Sunday, the 16th of Iyar. That was when their supplies taken from Egypt ran out.
The day didn’t have to coordinate with the date.
You mean, the day of the week. And that is true. So there must have been about 4 weeks until manna. And water, too, just before it.
Reading this passage, the seventh day became the first Holy Sabbath. On the sixth day Moses said:
"And he said unto them, This is that which the LORD hath said, To morrow is the rest of the holy sabbath unto the LORD: bake that which ye will bake to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning" (Ex. 16:23 AV).
Somebody must have figured a way to calculate the time from 14 Abib until then, eh?