Time zone conversions

[hanness]

Timezone conversions

Are there any time functions in QB64 that will help me to determine the time in another time zone?

As an example, if it is 10:00 PM on September 16, 2020, calculate the current time and date in the UK.

NOTE: The tricky part here is that the number of hours difference between the 2 locations varies because they don't both enter and exit daylight saving time on the same dates.

[bplus]

Try a "time zone" search.

Also might be in @SpriggsySpriggs API apps.

[Bert22306]

Timezone conversions
NOTE: The tricky part here is that the number of hours difference between the 2 locations varies because they don't both enter and exit daylight saving time on the same dates.

That's only one tricky part.

Time zones are quite unpredictable. In principle, they depend on longitude. In practice, the demarcations are quite jagged, subject to local policies in each country and sometimes even regions. For example, some states in the US do not use daylight saving time, while even adjacent states do. And, these policies change, over time.

I don't see any other way than to look it up, and to make sure you have up to date info.

[luke]

Obligatory Tom Scott video:

[bplus]

Is this why I everything I read last night is marked "New" again here at this forum?

[Richard Frost]

Some airports have a wall of clocks like this.  As noted above, a simple constant offset
from Greenwich isn't accurate.  Shucks. 

Code: QB64: [Select]

1. _TITLE "World Clock"
2. DEFINT A-Z
3. DIM p$(30), t!(30), t$(30), x(1), y(1)
4. SCREEN _NEWIMAGE(640, 480, 32)
5. black& = _RGB32(0, 0, 0)
6. green& = _RGB32(0, 200, 0)
7. white& = _RGB32(200, 200, 200)
8. FOR i = 1 TO 30: READ p$(i), t!(i): NEXT i
9.  
10. begin:
11. t$ = TIME$
12. h = VAL(MID$(t$, 1, 2)) + 7 '                    GMT = local + 7
13. m = VAL(MID$(t$, 4, 2))
14. IF h > 24 THEN h = h - 24
15. FOR i = 1 TO 30 '                                actual time for each place
16.     th = h + INT(t!(i))
17.     z! = ABS(t!(i)) - ABS(INT(t!(i)))
18.     tm = m + z! * 60 * SGN(t!(i))
19.     IF tm < 0 THEN tm = tm + 60: th = th - 1
20.     IF tm > 59 THEN tm = tm - 60: th = th + 1
21.     IF th < 0 THEN th = th + 24
22.     IF th > 23 THEN th = th - 24
23.     th$ = RIGHT$("0" + LTRIM$(STR$(th)), 2)
24.     tm$ = RIGHT$("0" + LTRIM$(STR$(tm)), 2)
25.     t$(i) = th$ + tm$
26. NEXT i
27. sort:
28. sorted = 1
29. FOR i = 1 TO 29
30.     s = 0
31.     IF stype = 0 THEN '                          place
32.         IF p$(i) > p$(i + 1) THEN s = 1
33.     ELSE '                                       time of day
34.         IF t$(i) > t$(i + 1) THEN s = 1
35.     END IF
36.     IF s THEN
37.         SWAP p$(i), p$(i + 1) '                  place
38.         SWAP t!(i), t!(i + 1) '                  zone
39.         SWAP t$(i), t$(i + 1) '                  time
40.         sorted = 0
41.     END IF
42. NEXT i
43. IF sorted = 0 THEN GOTO sort
44. d = 33: p = 0 '                                  distance, place index
45. FOR yc = 42 TO 402 STEP 90 '                     x center
46.     FOR xc = 70 TO 570 STEP 100 '                y center
47.         x1 = xc - d - 18: y1 = yc - d
48.         x2 = xc + d + 18: y2 = yc + d + 18
49.         LINE (x1, y1)-(x2, y2), black&, BF '     erase old
50.         p = p + 1 '                              place index
51.         _PRINTSTRING (xc - _PRINTWIDTH(p$(p)) \ 2, yc + d + 4), p$(p)
52.         CIRCLE (xc, yc), d, green&
53.         IF VAL(LEFT$(t$(p), 2)) < 12 THEN PAINT (xc, yc), green&, green& ' am/pm
54.         FOR a = 0 TO 360 STEP 30 '               clock tick marks
55.             x1 = xc + (d - 3) * COS(_D2R(a))
56.             y1 = yc + (d - 3) * SIN(_D2R(a))
57.             CIRCLE (x1, y1), 1, white& '         ticks
58.         NEXT a
59.         th = VAL(MID$(t$(p), 1, 2)) '            hour
60.         tm = VAL(MID$(t$(p), 3, 2)) '            minute
61.         r! = _D2R(tm * 6 - 90) '                 minute hand
62.         x(0) = xc + (d - 8) * COS(r!)
63.         y(0) = yc + (d - 8) * SIN(r!)
64.         r! = _D2R((th + tm / 60) * 30 - 90) '    hour hand
65.         x(1) = xc + (d - 16) * COS(r!)
66.         y(1) = yc + (d - 16) * SIN(r!)
67.         FOR zz = 0 TO 1 '                        draw hands
68.             FOR zx = -1 TO 1
69.                 FOR zy = -1 TO 1
70.                     LINE (xc + zx, yc + zy)-(x(zz), y(zz)), white&
71.                 NEXT zy
72.             NEXT zx
73.         NEXT zz
74.     NEXT xc
75. NEXT yc
76. t$ = LEFT$(TIME$, 5)
77. LINE (10, 470)-(630, 471), black&, BF '           erase seconds bar at bottom
78. DO: _LIMIT 10
79.     x = VAL(RIGHT$(TIME$, 2)) * 10 + 20
80.     LINE (10, 470)-(x, 471), green&, B '          seconds bar
81.     i$ = INKEY$
82.     IF i$ = CHR$(27) THEN SYSTEM '                Esc to quit
83.     IF i$ = " " THEN stype = 1 - stype '          spacebar changes sort (time or place)
84. LOOP UNTIL (t$ <> LEFT$(TIME$, 5)) OR (i$ > "")
85. GOTO begin
86.  
87. DATA Amsterdam,1
88. DATA Beijing,8
89. DATA Berlin,1
90. DATA Brasilia,-3
91. DATA Cairo,2
92. DATA Chicago,-6
93. DATA Delhi,5.5
94. DATA Denver,-7
95. DATA Detroit,-5
96. DATA Edmonton,-7
97. DATA Gander,-3.5
98. DATA Hawaii,-10
99. DATA Hong Kong,8
100. DATA Houston,-6
101. DATA Istanbul,2
102. DATA London,0
103. DATA Los Angeles,-9
104. DATA Madrid,1
105. DATA Mexico City,-6
106. DATA Moscow,3
107. DATA New York,-5
108. DATA Paris,1
109. DATA Perth,8
110. DATA Phoenix,-8
111. DATA Rome,1
112. DATA Seoul,9
113. DATA Singapore,8
114. DATA Sydney,10
115. DATA Tehran,3.5
116. DATA Tokyo,9
117.  
118.  

[SpriggsySpriggs]

I don't remember if I have something in my API collection but here is a link to a post where I asked a similar question about conversion for time zones and got some help on that. I use it for programs that I make. It could be in my API collection in my NASA one. Anyways, here is the link:
https://www.qb64.org/forum/index.php?topic=2823.msg121099#msg121099

[bplus]

Ah must of been that I was remembering, thanks Spriggsy.

@Richard Frost nice little app!

[hanness]

Thanks for the help!