19. The computer system of claim 16 , wherein the confidence value for a respective date format is further based on an amount of specificity of the respective date format, the amount of specificity of the respective date format being selected from the group consisting of: a number of unknown variables of in the respective date format; a precision of the respective date format.
16. A computer system for resolving ambiguities in date values associated with an attribute of an entity, the computer system comprising: one or more processors; memory; and one or more programs stored in the memory, the one or more programs comprising instructions to: obtain a first text string associated with an attribute of an entity, wherein the first text string is extracted from a first web document; determine if that the first text string conforms to one or more date formats; assign a first confidence value for each of the date formats for the first text string based on a first number of unknown variables that remain when interpreting the first text string using each of the date formats; obtain a second text string associated with the attribute of the entity, wherein the second text string is extracted from a second web document; determine if that the second text string conforms to one or more date formats; assign a second confidence value for each of the date formats for the second text string based on a second number of unknown variables that remain when interpreting the second text string using each of the date formats; determine a first date string expressed in a date format with a highest first confidence value for the first text string; determine a second date string expressed in a date format with a highest second confidence value for the second text string; and merge a first subset of the first date string and a second subset of the second date string to obtain a date value for the attribute.