Аннотация:The authors propose a method for estimation of the time delay between identical time samples with unequidistant data. They have analyzed Vanderriest's (1989) and Schild's (1990) photometric observations of Q 0957+561 A,B, the first gravitational lens. The time delay is found to be 1.45±0.04 years. Using the Monte-Carlo simulations they compare reliability of time delay determination methods and define that the confidence level of their result is better than 99%. The problem of microlensing effects is briefly discussed.