1. Date of third (and final) vote = the date the parliament has voted a bill as law
2. Date of publication (for technical reasons this might not coincide with the vote date)
3. Date of validity - a bill is usually passed with a date of validity, between the date of publication and validity the bill is not formally law yet. Sometimes there are separate dates of validity for separate parts of the bill. To make matters more complicated, dates of validity can be changed when the bill designates government ministers with the authority to change them (the dates).
Also, in Israel many laws never "make it" to their date of validity since the yearly Law of Arrangements (http://www.knesset.gov.il/lexicon/eng/hesderim_eng.htm) decides which laws passed in the previous year have proper funding, such that officially some laws get "punted" into the future, possibly indefinitely. It gets quite confusing because from a legal point of view, the dates that are relevant to the justice system (as in, when a bill is relevant or not to the court) are usually the date of voting, whereas when it comes to government the third date is the important one.
We are still moving forward with our initiative, but it seems that for now there are no version control systems which are a good solution to the law management problem.
(edited for formatting)