1. A method comprising: receiving a request to store a value in a record of a database, wherein the request comprises a single expression that includes a database command and temporal metadata, wherein the database command causes the value to be stored and comprises discriminator information that identifies stored data comprising the value, and wherein the temporal metadata is marked according to a syntax that separates the temporal metadata from the database command, wherein the temporal metadata specifies a time and a manner in which the value should change; in response to receiving the request, executing the single expression at least in part by: executing the database command to store the value in the record of the database, and storing, based at least in part on the temporal metadata and the discriminator information, first information that indicates the specified time and second information that indicates the specified manner and that identifies the stored data; after an amount of time has passed: based on the first information that indicates the specified time, determining whether a current time satisfies the specified time; in response to determining that the current time satisfies the specified time, changing the value stored in the record of the database in the specified manner based on the second information that indicates the specified manner and that identifies the stored data; wherein the method is performed by one or more computing devices.