Theme: Timely - SPRING is placed ahead of the last word in the theme answers.
20A. Have things finally go one's way: CATCH A BREAK. Spring Break.
36A. Mosquito-borne disease: YELLOW FEVER. Spring Fever.
42A. Engage in hard-nosed negotiations: PLAY CHICKEN. Spring Chicken.
56A. Make an annual clock adjustment ... and what the end of 20-, 36- and 42-Across may literally have: SPRING AHEAD
Argyle here. Bill is averaging a puzzle a year.
1. Easy thing to do: SNAP
5. Lobster serving: CLAW
9. Great time: BLAST
14. Skin opening: PORE
15. Tra-__: refrain syllables: LA-LA
16. Main artery: AORTA
17. Snapchat co-founder Spiegel: EVAN. Only 27 years old.
18. Cyberzine: eMAG
19. Parakeets' quarters: CAGEs
23. Photo __: media events: OPS
24. Charged particles: IONs
25. Intl. news broadcaster: VOA. (Voice of America)
27. Singer's quavers: TRILLS
30. Recently: AS OF LATE
35. Harry's pal Weasley: RON. Harry Potter books.
38. Penne __ vodka: ALLA. Penne alla vodka is a pasta dish made with vodka and penne pasta, usually made with heavy cream, crushed tomatoes, onions, and sometimes sausage, pancetta or peas. Wikipedia
40. Singer Damone: VIC
41. Trig ratio: SINE
47. "Just a __!": SEC
48. Dress-for-success accessory: POWER TIE
49. New York Giants legend with 511 career home runs: MEL OTT. Cool! Whole name.
51. Used a bench: SAT
52. Location: SITE
53. Sponsors' spots: ADs
62. Georgia state fruit: PEACH. But do you dare eat a peach?
64. Smell: ODOR
65. Gold rush animal: MULE
66. "Orange" tea grade: PEKOE
67. Kind of pittance?: MERE
68. The "A" of NEA: ARTS. (National Endowment for the Arts)
69. Drive too fast: SPEED
70. New England NFLers: PATS
71. Barnes & Noble reader: NOOK
1. Job detail, for short: SPEC. Specification.
2. Old Chevy: NOVA. Production: 1961–1979; 1985–1988. The 1985-88 Chevrolet Nova was a joint venture between General Motors and Toyota.
3. "I smell __!": A RAT
4. Crossword solver's choice: PENCIL
5. Remove dirt from: CLEANSE
6. Petting zoo youngsters: LAMBS
7. Bygone apple spray: ALAR
8. Regular pay: WAGE
9. "Not so close!": "BACK OFF!"
10. Extended pd. away from work: LOA. (Leave Of Absence)
11. Golden Fleece ship: ARGO
12. How-to instruction: STEP
13. Soviet news agency: TASS. Founded in 1902, Tass is the fourth largest major news agency.
21. Sanctified: HOLY
22. Declare emphatically: AVOW
26. Drinks in schooners: ALES
27. Maria von __, family singers' matriarch: TRAPP
|Trapp Family Lodge, Stowe, Vermont|
28. Rich boy in "Nancy" comics: ROLLO
29. Groom's new relative: IN-LAW
30. Author Hoffman: ALICE. Bio.
31. Foot cover: SOCK
32. French dispatch boat: AVISO. An oldie but goodie.
33. Guiding principle: TENET
34. Standing tall: ERECT
37. Heinz varieties count, to Caesar?: LVII. (57)
39. Those in favor: AYEs
43. Failed suddenly, as a laptop: CRASHED
44. URL letters: HTTP. URL yesterday, HyperText Transfer Protocol today.
45. Political fugitives: ÉMIGRÉS
46. __ profit: make money: NET A
50. __ Brothers: defunct financial firm: LEHMAN
52. Equine outburst: SNORT. Play this good and loud; see who comes to find out what is happening.
53. iPhone downloads: APPs
54. __-sea diver: DEEP
55. Drink with sushi: SAKE
57. Frolic in a lively way: ROMP. Too much sake?
58. Thinking output: IDEA
59. Currency named for a continent: EURO
60. Choir voice: ALTO
61. Student's workplace: DESK
63. Runner Sebastian: COE. He ran a sub-4-minute mile. Roger Bannister was the first person to run a mile under 4 minutes. He died Saturday.