In NRSV, NJB, and AV (John 19: 31) this was the day before a religious festival, or any Sabbath, when it was necessary to get things ready on account of the law ordering cessation from all work on the Sabbath itself.
Citation for preparation
Citation styles are based on the Chicago Manual of Style, 15th Ed., and the MLA Style Manual, 2nd Ed..
MLA
"preparation." In A Dictionary of the Bible. Ed. W. R. F. Browning. Oxford Biblical Studies Online. May 20, 2013. <http://www.oxfordbiblicalcstudies.com/article/opr/t94/e1520>.
Chicago
"preparation." In A Dictionary of the Bible. , edited by W. R. F. Browning. Oxford Biblical Studies Online, http://www.oxfordbiblicalcstudies.com/article/opr/t94/e1520 (accessed May 20, 2013).