If one vows I'tikaf for a month, is continuous observance required?

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If one vows I'tikaf for a month, it means one lunar month or thirty days. The obligation of sequence (tatabu') is subject to a difference of opinion. One opinion holds that sequence is not required, similar to the ruling on vowed fasting, as fasting is valid when interspersed. The opposing view holds that sequence is obligatory because the term implies continuation, similar to an oath regarding conversation or the waiting period (Iddah). If one observes a month between two crescent moons, it suffices, even if incomplete in days. If one observes thirty days across two months, it is valid, and the nights are included because 'month' refers to both day and night.