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For investment performance, the Money Weighted Return is often used as an approximation of the Time Weighted Return. A common method for calculating an approximate Money Weighted Return is the Modified Dietz.
The Modified Dietz method overcomes the need to know the valuation of the portfolio on the date of each cash flow by assuming a constant rate of return during the period. Each cash flow is weighted by the amount of time it is held in the portfolio. The Modified Dietz method assumes that net contributions are invested at the end of the respective day they occur.