The BIASDATE field operator works in a similar way to the BIAS field operator. It allows you to bias the score of results at query time according to the proximity of the specified field to a particular date.

Specify BIASDATE in the format:



optimumDate is the date that the field must contain to increase or decrease the result weight by the maximum percentage. See Date formats for a list of the available date formats.
range is a positive value that determines the range in seconds of the specified optimum. If the specified field contains a value that is in the range (optimumrange) to (optimum + range), the result weight is increased or decreased according to the specified percentage.
percentage is a percentage in the range –100 to 100. If the value of the specified field is within the specified range, the score of the result increases or decreases according to how close the value is to the specified optimum. When you set Absweight to True, this is the absolute value by which to boost the weight, and it is then not limited by +/– 100.
yourFields are one or more fields. A document has its score boosted if it contains one of these fields, and if this field contains a date that falls within the specified range of the optimum date. Separate multiple fields with colons (:). There must be no space before or after a colon.

For example: