
902 So.2d 351 (2005)
Patrick SMITH, Appellant,
v.
STATE of Florida, Appellee.
No. 5D05-992.
District Court of Appeal of Florida, Fifth District.
May 27, 2005.
Patrick Smith, Lake City, Pro Se.
No Appearance for Appellee.
MONACO, J.
The appellant, Patrick Smith, appeals the denial of his Rule 3.800(a) Motion to Correct Illegal Sentence in which he sought additional gain time jail credit for time served after his sentencing date in county jail, as opposed to state prison. We affirm for two reasons.
First, the calculation of gain time is a function of the Department of Corrections, through which relief must first be pursued administratively. While Rule 3.800(a) provides a vehicle for criminal defendants to address the issues of an illegal sentence, or an incorrect calculation of a scoresheet, or a sentence that does not grant proper credit for time served prior to sentencing, it is not available to address post-sentencing jail credit or gain time issues. See Gaynor v. State, 831 So.2d 1246 (Fla. 5th DCA 2002); Tarrand v. State, 809 So.2d 66 (Fla. 5th DCA 2002). See also Brown v. State, 427 So.2d 821 (Fla. 2d DCA 1983).
Second, the motion filed in the trial court and the documents filed in this appeal are legally insufficient. There is no explanation, for example, of why Mr. Smith spent the time in jail for which he seeks gain time.
AFFIRMED.
PETERSON and PLEUS, JJ., concur.
