Mohammed founded the religion of Islam in CE 610.

As to what constitutes being IN the Islamic Period, it depends upon context and the beliefs of the person writing. I expect most Muslims would say we are still in the Islamic Period.

As a practical designation, "the Islamic Period" encompasses the 7th C. up to the year 1400. This is most useful when we are discussing glass manufacture. However, we should always remember that glass was invented in Western Asia, and continuously made there for some 4,000 years. The beads that were made just prior to the time of Mohammed were not profoundly different. So the designation does not exclude somewhat earlier beads, that might also be conveniently designated as "Post-Roman Period" beads.

In 1400, the native glass industries of the Eastern Mediterranean lands (particularly Aleppo and Damascus), were destroyed by Tamerlane's armies. This was also the time of the rise of Venice in Europe, and its involvement in making glass products—including many beads—that were exported abroad, including to the Eastern Mediterranean lands—thus filling the void.

In terms of glass production, I refer to "Early Islamic Period" as encompassing the 7th through the 10th Cs., and the "Late Islamic" as the 11th through the 14th Cs.—an 800-year span, divided into two 400-year segments. However, in terms of beadmaking, there's very little we can say about particular beads (whether early or late).

It has only been over the past two decades that anyone has promoted Islamic Period beads as as being the specific products they are. And I have been one of the primary proponents of this recognition (beginning in about 1983). Prior to that time, most Islamic Period beads were mistakenly and routinely called "Roman beads."

It is also a point I stress often that the designation "Roman bead" is misleading, and usually suggests or promotes some backwards thinking. Romans did not make glass beads, per se, though they did appropriate industries, move artisans around, and change distribution patterns. But if we think of an Egyptian bead from CE 100 as "Roman," this makes about as much sense as calling a Han (Chinese) bead from CE 100 as a "Roman bead." Consequently, I always remark (and encourage others to say) that appropriate beads "are from the Roman Period." These beads would have been made in the Middle East whether the Romans had ever been there or not (!). Crediting the Romans with their manufacture is a travesty of history.

And, as I view and promote it, the year CE 1400 also marks the end of "ancient glass-beadmaking" and the beginning of "modern glass-beadmaking." Not everyone agrees with me—but I find this logical, practical, and useful.

I hope this helps.