[HarryT]

OK, very briefly then:

Years were numbered starting from 1 for the reign of each new king. There were three seasons reflecting the agricultural year: "akhet" ("inundation", when the Nile flooded), "peret" ("growing", when crops were grown), and "shemu" ("harvest").

Each season had 4 months of 30 days each, divided into three 10-day weeks.

That makes 360 days, so to make the year up to the correct 365 days, there were 5 extra days at the end of the year which were not in any month.

Dates were written as the "regnal year" of the king, followed in turn by month number, season, and day number, so a date would be something like "year 15, 3rd month of harvest, day 8".

As you rightly say, numbers themselves were written a little like Roman numerals, on a decimal system, so there were symbols for:

1: a single stroke
10: an upside-down "U"
100: a coil of rope
1000: a lotus flower
10,000: a finger
100,000: a tadpole

and you just repeated each symbol the appropriate number of times, from the largest unit down to the smallest, so the number "35" was written "UUUIIIII" (with the "U's" upside down.)

There was also a method of expressing fractions, which was rather complex and I won't go into it.

Hope that helps,