Calendar rebalancing is the most rudimentary rebalancing approach. This strategy simply involves analyzing the investment holdings within the portfolio at predetermined time intervals and adjusting to the original allocation at a desired frequency. Monthly and quarterly assessments are typically preferred because weekly rebalancing would be overly expensive while a yearly approach would allow for too much intermediate portfolio drift. The ideal frequency of rebalancing must be determined based on time constraints, transaction costs and allowable drift.
A major advantage of calendar rebalancing over formulaic rebalancing is that it is significantly less time consuming for the investor since the latter method is a continuous process.