9. A system, comprising: one or more computers programmed to perform operations comprising: obtaining search history data, the search history data including a first query; determining whether a different second query is temporally related to the first query based on calculated time-based query-to-query transition probabilities including a query-to-time transition probability between the first query and a time of year and a time-to-query transition probability between the time of year and the second query, where the query-to-time transition probability between the first query and the time of year estimates a strength of a relationship between the first query and the time of year, wherein determining the query-to-time transition probability comprises: determining whether the first query has a significant increase in popularity at the time of year; and if the first query does have a significant increase in popularity at the time of year, determining the query-to-time transition probability as a function of the number of times the query had a significant increase in popularity at the time of year; and modifying scoring data for one or more documents responsive to the second query to favor newer documents responsive to the second query based on the calculated time-based query-to-query transition probabilities.
9. A system, comprising: one or more computers programmed to perform operations comprising: obtaining search history data, the search history data including a first query; determining whether a different second query is temporally related to the first query based on calculated time-based query-to-query transition probabilities including a query-to-time transition probability between the first query and a time of year and a time-to-query transition probability between the time of year and the second query, where the query-to-time transition probability between the first query and the time of year estimates a strength of a relationship between the first query and the time of year, wherein determining the query-to-time transition probability comprises: determining whether the first query has a significant increase in popularity at the time of year; and if the first query does have a significant increase in popularity at the time of year, determining the query-to-time transition probability as a function of the number of times the query had a significant increase in popularity at the time of year; and modifying scoring data for one or more documents responsive to the second query to favor newer documents responsive to the second query based on the calculated time-based query-to-query transition probabilities. 16. The system of claim 9 , wherein the time-to-query transition probability between the time of year and the second query is determined according to: P tran ⁡ ( t B , q B ) = peak ⁡ ( q B , t B ) ∑ q i ∈ S q ⁢ peak ⁡ ( q i , t B ) wherein P tran (t B , q B ) is the transition probability between the time of year and the second query, peak(q, t) has a value of 1 if the second query had an increase in popularity at the time of year and otherwise is 0, and S q is a set of queries in a search history data.