There are two historically important cases of this empirically regulated intercalation of months, which must be dealt with in detail, since they are much debated. The dispute has arisen from a failure to recognise the empirical intercalation and its workings. The one case is that of the old Arabian calendar before Mohammed, the other that of the Babylonian calendar. The old Arabian names of months depend in great measure, as has been shewn already[907], upon the seasons. Originally therefore the months must have been connected with the solar year, and must have been approximately fixed in their position by the sufficiently familiar empirical method. The same thing is shewn by the naming of the last months from the pilgrimage to Mecca. In pre-Mohammedan times the pilgrimages were at the same time business journeys; trade and cult were, as so often, united, and commercial intercourse was first made really possible when by religious sanction a time of peace was established during which journeys to and fro could be taken in safety. The first month of the peace of God is _dhu-l-qa’da_, and _dhu-l-hijja_ is the month of the gathering in Mecca: the following month, _safar I_, was also included in the time of peace, and was therefore called _muharram_. During all three months there were fairs: in the neighbourhood of Mecca there was a whole succession of them, following upon each other in _dhu-l-qa’da_ and _dhu-l-hijja_; in _safar_ there was a corn-market in Yemen[908]. The gay life of the great fair of Mecca is described in detail in old Arabic sources; it seems to have drawn the people almost more than the religious ceremonies, and first gave Mecca its real importance. An annual fair is however dependent upon the seasons, both on account of the journeys and for the products bought and sold. Sprenger has already remarked that the winter months are quite unsuitable for merchants’ journeys to Syria, and that in the late summer it was not to be expected that corn which had been cut at the beginning of March should be taken in to the markets[909]. Because of the markets that were held in them, the months must also have had a fixed position in the solar year. This importance of Mecca explains why the Meccan months became so wide-spread. The two names _dhu-l-qa’da_ and _dhu-l-hijja_ are formed with _dhu_, differently from the others, and were coined at Mecca. This leads to the conclusion that these names were innovations occasioned by the business intercourse of that city.