Use special sessions for term start dates

[bycoffe]

This corrects term start dates in historical terms, to use, by default, the beginning of the first session of each Congress, even if it's a special session. See #388.

This makes the following changes to start dates:

 2nd Congress 1791-10-24 => 1791-03-04
 3rd Congress 1793-12-02 => 1793-03-04
 4th Congress 1795-12-07 => 1795-06-08
 5th Congress 1797-05-15 => 1797-03-04
 7th Congress 1801-12-07 => 1801-03-04
 9th Congress 1805-12-02 => 1805-03-04
11st Congress 1809-05-22 => 1809-03-04
15th Congress 1817-12-01 => 1817-03-04
17th Congress 1821-12-03 => 1821-03-06
21st Congress 1829-12-07 => 1829-03-05
27th Congress 1841-05-31 => 1841-03-04
29th Congress 1845-12-01 => 1845-03-04
31st Congress 1849-12-03 => 1849-03-05
32nd Congress 1851-12-01 => 1851-03-05
33rd Congress 1853-12-05 => 1853-03-04
35th Congress 1857-12-07 => 1857-03-04
36th Congress 1859-12-05 => 1859-03-04
37th Congress 1861-07-04 => 1861-03-04
38th Congress 1863-12-07 => 1863-03-04
39th Congress 1865-12-04 => 1865-03-04
43rd Congress 1873-12-01 => 1873-03-04
44th Congress 1875-12-06 => 1875-03-05
45th Congress 1877-10-15 => 1877-03-05
47th Congress 1881-12-05 => 1881-03-04
49th Congress 1885-12-07 => 1885-03-04
51st Congress 1889-12-02 => 1889-03-04
53rd Congress 1893-08-07 => 1893-03-04
55th Congress 1897-03-15 => 1897-03-04
57th Congress 1901-12-02 => 1901-03-04
58th Congress 1903-11-09 => 1903-03-05
59th Congress 1905-12-04 => 1905-03-04
61st Congress 1909-03-15 => 1909-03-04
63rd Congress 1913-04-07 => 1913-03-04
65th Congress 1917-04-02 => 1917-03-05
67th Congress 1921-04-11 => 1921-03-04
69th Congress 1925-12-07 => 1925-03-04
71st Congress 1929-04-15 => 1929-03-04
73rd Congress 1933-03-09 => 1933-03-04

The dates are based on the GovTrack sessions.tsv file.

I made the changes using this script: https://gist.github.com/bycoffe/b8fdc86dcc0eb26022cf6a38e4286512

[JoshData]

This PR conflicts with your previous one (I think that's the cause of the conflict). Can you re-do?

[bycoffe]

Should be fixed.

[JoshData]

I wonder if we shouldn't trust my session data. According to http://content.time.com/time/politics/article/0,8599,2009480,00.html, it may be that only one chamber or the other was in session during a special session, and so that might change what we want to adjust the dates to. Or maybe it doesn't matter.

[bycoffe]

That's a good point. The Senate has these two PDFs on its site, one of which has Senate special sessions and one of which has special sessions of both chambers. We could use these as a guide.

My concern with using only the regular sessions is that we'll end up leaving out entire terms for legislators who only served during a special session (because they left before the start of the first regular session because of resignation or death).

[JoshData]

I think we're also missing some who were elected to fill a vacancy after the end of the last session.

I don't mind missing people who didn't actually serve, but I totally agree that if they served they should be in the data.

[bycoffe]

As far as I can tell there are no official records of swearing-in dates for the older sessions. The Senate does have a list of "start of service" dates, but the historian's office says these are not always the same as the date the senator was sworn in. It also appears that for at least some representatives, the start of service listed in Bioguide is the first date of the term's Senate special session (even if the House did not go into session until later).

So it seems like for cases where the swearing-in date is unknown, the choices for default term start dates are:

• Use the first date of the term's first regular session. This is mostly what the data uses now. In years when there was a special session before the first regular session, many/most members' start dates are incorrect, since they would have started at the beginning of the special session. This also leaves out some members' terms entirely (if they served for part/all of a special session but none of the regular session); these cases would have to be fixed manually anyway, but it would lead to lots of inconsistencies in start dates.

• For House terms, use the first date of the House's first special session (if it was before the first regular session). For Senate terms, use the senator's start date (listed here: http://www.senate.gov/artandhistory/history/resources/pdf/chronlist.pdf and in Bioguide).

[JoshData]

For House terms, use the first date of the House's first special session (if it was before the first regular session). For Senate terms, use the senator's start date (listed here: http://www.senate.gov/artandhistory/history/resources/pdf/chronlist.pdf and in Bioguide).

+1

[JoshData]

Should we just merge this and then come back to cases where only one chamber was in session during the special session in a later issue/PR?

[bycoffe]

I was still planning to change it to use separate start dates for each chamber. I'd be fine with either merging this and then changing it or leaving the dates as they are and making a new PR...whatever you think is best. 

[JoshData]

Ok that's fine. If you're still working on it, no hurry.