T he farm bill provides an opportunity for Congress to address agricultural and food issues comprehensively about every five years. Over time, farm bills have tended to become more complicated and politically sensitive. This has made the timeline for reauthorization less certain. Recent farm bills have been subject to developments that have delayed enactment, such as insufficient votes to pass the House floor, presidential vetoes, and short-term extensions. The Agriculture Improvement Act of 2018 ( P.L. 115-334 ), often called the "2018 farm bill," was enacted on December 20, 2018. In the House, the Agriculture Committee reported the bill on April 18, 2018. An initial floor vote on May 18 failed by 198-213, but procedures allowed that vote to be reconsidered ( H.Res. 905 ). The House passed H.R. 2 in a second vote of 213-211 on June 21. In the Senate, the Agriculture Committee reported its bill ( S. 3042 ) on June 13, 2018, by a vote of 20-1. The Senate passed its bill as an amendment to H.R. 2 by a vote of 86-11 on June 28. Conference proceedings officially began September 5 and concluded on December 10. The 1973 farm bill was enacted less than 3 months after being introduced. In contrast, the 2014 farm bill took more than 21 months from introduction to enactment, spanning two Congresses. The House rejected a bill in 2013 and then passed separate farm and nutrition assistance components—the first time a chamber-passed farm bill did not include a nutrition title since 1973. The House later procedurally recombined them for conference with the Senate. Both the 2002 and 2008 farm bills had expired for about three months (from October through December in 2007 and 2012) before extensions were enacted. In each case, the fiscal year began under a continuing resolution for appropriations. The extensions of the 2002 farm bill were for relatively short periods totaling about five months during final House-Senate negotiations. However, the extension of the 2008 farm bill in 2013 was for a full year. This report examines the major legislative milestones for the last 12 farm bills over 54 years, a period representing modern farm bills with growing complexity. Table 1 contains a history of major legislative action on farm bills since 1965. Figure 1 shows the major dates on a timeline. Different parts of a farm bill are authorized for different periods of time. Fiscal years, calendar years, and crop years can be important to different programs. Programs authorized by the 2018 farm bill (the Agriculture Improvement Act of 2018) would generally expire either at the end of FY2023 (September 30, 2023) or after the 2023 crop year, which varies among crops. Enacting farm bills after the end of the final fiscal year for which programs have been authorized has been a common occurrence. In the past 42 years covering the nine farm bills since 1976—when the federal government began using a fiscal year that began on October 1 —only the 1977 and 2002 farm bills were enacted before the September 30 expiration date for programs that would have been affected by the fiscal year. The 1981, 1985, 1990, and 2018 farm bills were enacted within three months after the final fiscal year for which programs were authorized ended. The 1996 farm bill was enacted in April 1996 following the September 30, 1995, expiration of some of the authorizations in the 1990 farm bill. The 2008 and 2014 farm bills were enacted well after their original September 30 expirations and following the enactment of extensions. Expiration at the end of a fiscal year (September 30) matters for programs with fiscal year authorizations. These programs include certain nutrition, conservation, and trade programs; various agricultural programs, excluding the Title I commodity programs; and many authorizations for discretionary appropriations. The consequences of expiration of a farm bill are discussed in other CRS reports. All farm bills since 1965—except the 2008 and 2014 farm bills—have been enacted before December 31 in the year of their expirations . Therefore, only the 2008 and 2014 farm bills have required extensions (see " Short-Term Extensions " below). From another perspective, the 1990 farm bill was the last farm bill prior to the 2018 farm bill that was enacted by December 31—within three months from the start of fiscal-year expiration but before the spring-planted crops covered by the new law were planted. The 1996, 2002, 2008, and 2014 farm bills were enacted in a calendar year after their introduction—in April (1996), May (2002), June (2008), and February (2014)—but still prior to the first crop covered by the farm bill being harvested. Expiration at the end of a calendar year matters mostly for the dairy program, one of the farm commodity programs in Title I of recent farm bills. The farm commodity programs are tied to crop years—that is, the year in which a crop is harvested—and dairy is the first commodity that would be affected by reverting to "permanent law," since its crop year begins on January 1 after the year of expiration. Since 1965, 8 out of 12 enacted farm bills were introduced in the first session of a two-year Congress (the odd-numbered year). The other four (1970, 1990, 2014, and 2018) were introduced in the second session of a two-year Congress (the even-numbered year). The 2018 farm bill was the first time since before 1965 that both chambers completed floor action before the end of June. Of the four bills introduced in a second session, the 1970, 1990, and 2018 farm bills were enacted during a lame duck Congress (after an election) in November and December of the same year. The 2014 farm bill, which was introduced in 2012, was the first farm bill to start in one Congress, remain unfinished, and require reintroduction in a subsequent Congress. The House and Senate have taken turns in initiating action on a farm bill. Since 1965, the Senate was first to mark up farm bills in 1973, 1977, 1981, 2012, and 2013. The House was first to mark up bills in 1965, 1970, 1985, 1990, 1995 (and 1996), 2001, 2007, and 2018. Extensions of a prior farm bill while its successor is being written have been atypical. Only the 2002 and 2008 farm bills have required extensions in 2007-2008 and 2013, respectively, as their successors were being written. When the 2002 farm bill expired, portions of it were extended six times for less than a year total beginning in December 2007. When the 2008 farm bill expired, the entire farm bill was extended in January 2013 for all of FY2013 and the 2013 crop year. While the 2014 farm bill was expired from October 1 until the 2018 farm bill was enacted, the continuing resolution for appropriations continued many operations, though some new program activity ceased. Presidential vetoes of farm bills are not common. Since 1965, only the 2008 farm bill has been vetoed as stand-alone measure; it was vetoed twice. A 1995 farm bill was vetoed as part of a larger budget reconciliation package. President George W. Bush vetoed the 2008 farm bill ( H.R. 2419 ). When Congress overrode the veto to enact P.L. 110-234 , it accidentally enrolled the law without Title III (the trade title). Congress immediately reintroduced the same bill with the trade title ( H.R. 6124 ). President Bush vetoed this version as well, and Congress again overrode the veto to enact P.L. 110-246 , a complete 2008 farm bill that included the trade title. The overrides in 2008 were the only time that a farm bill was enacted as a result of a veto override. President Clinton vetoed a 1995 budget reconciliation package that included the first version of what became the 1996 farm bill, but the veto was not due to the farm bill itself but rather the controversial nature of the reconciliation bill in which the farm bill was embedded. Prior to 1965, the first veto of a farm bill was in 1956, when President Eisenhower vetoed H.R. 12 (84 th Congress), the first version of the Agricultural Act of 1956. As farm bill reauthorization has tended to become more complex and engender greater political sensitivity, the process of enacting a new farm bill prior to the expiration of the existing law has become more difficult. As stakeholders in the farm bill have become more diverse, more people are affected by the legislative uncertainty around this process. This lack of certainty may translate into questions about the availability of future program benefits, some of which may affect agricultural production decisions or market uncertainty for agricultural commodities.