(a) The indebtedness for labor performed by the day or week accrues at the end of each week during which the labor is performed.
(b) The indebtedness for material or services accrues on the date the material or services were last furnished. All material or services that a person furnishes for the same land, leasehold interest, oil or gas pipeline, or oil or gas pipeline right-of-way are considered to be furnished under a single contract unless more than six months elapse between the dates the material or services are furnished.