[R] Datetime misrepresented on x-axis of a multiple plot

[Ogbos Okike]

Dear Contributors,
I am trying to do a plot with multiple y-axis on a common x-axis. I have
made some progress but I am having difficulties with datetime appearing on
x-axis. Instead of as date, it appears as large numbers.

Sample of my data:
78 09 28  0 6.7 -40.4 -3.5 2.3 -3.6 278036 5.8 612
78 09 28  1 5.7 7.3 -4.4 1.4 0.6 261169 4.9 623
78 09 28  2 5.6 -20.9 -3.6 3.1 -1.8 269323 4.8 625
78 09 28  3 5.8 -46.9 -3.4 0.2 -3.6 254221 4.7 626
78 09 28  4 6.2 -41.4 -3.9 1.2 -3.6 248567 4.2 618
78 09 28  5 6.1 -54.6 -3 1 -4.4 252669 4.4 629
78 09 28  6 NA NA NA NA NA 220480 4.3 606
78 09 28  7 7.1 26 -4.8 3.6 2.9 216887 4.4 613
78 09 28  8 7.1 -21.4 -4.7 3.5 -2.3 249928 4 643
78 09 28  9 7 -13.6 -2.7 5.2 -1.4 268806 4 656
78 09 28  10 6.6 -18.5 -3.7 3.6 -1.7 285608 4.2 651
78 09 28  11 6.7 -6.6 -2.1 4.7 -0.6 280446 4.2 661
78 09 28  12 6.7 -29.7 -1.9 4 -2.5 281928 4.2 659
78 09 28  13 6.2 -8.7 -2.1 4.7 -0.8 273465 4.4 651
78 09 28  14 6.1 31.8 -4.7 0.9 3 212374 4.2 631
78 09 28  15 5.4 9.3 -4.5 -0.9 0.8 219662 3.9 636
78 09 28  16 4.9 6.3 -4.5 -0.5 0.5 220610 3.8 628
78 09 28  17 4.7 4.5 -4.3 -0.6 0.3 214432 3.7 628
78 09 28  18 4.9 3.1 -4.5 0.3 0.2 202199 3.5 623
78 09 28  19 5 -13 -4.6 -0.3 -1.1 192859 3.2 619
78 09 28  20 5.1 -26 -3.5 2 -2 193868 3.1 627
78 09 28  21 10.1 -37.5 -5.1 4.9 -5.4 284122 5.9 683
78 09 28  22 8.4 -7.3 -3.6 5.5 -0.8 367499 6.2 694
78 09 28  23 8.2 -17.7 -4.7 4.4 -2.1 346644 4.9 689
78 09 29  0 8 6.3 -4.3 5.8 0.8 269569 4.7 708
78 09 29  1 8.6 35 -3 6.2 4.8 187132 3.2 709
78 09 29  2 8.1 24.8 -4.1 6 3.3 166644 3.5 689
78 09 29  3 15.9 29.6 -2.4 9.6 5.6 720902 6.6 866
78 09 29  4 14.9 18.9 -2.8 13.8 4.8 1587324 8.1 912
78 09 29  5 14.1 8.2 -10.2 8.3 1.9 1509336 8.1 871
78 09 29  6 15.6 -2.9 -6.1 11.5 -0.7 968890 7.8 878
78 09 29  7 19.6 -49.7 1.2 12.1 -14.4 574978 5.4 906
78 09 29  8 23.5 -44.2 -1.4 11.7 -11.5 287721 4.1 865
78 09 29  9 25.3 -71.8 -2.4 7.5 -23.9 58521 5.1 859
78 09 29  10 24.8 -63.1 -2.3 10.9 -22 74956 1.5 821
78 09 29  11 23.8 -50 -2 15.1 -18.1 64510 3 807
78 09 29  12 21.4 -34.3 0.1 17.6 -12 50247 2.3 795
78 09 29  13 18.4 -20 -2 17 -6.3 59939 2.9 802
78 09 29  14 16.4 -13.9 -2.8 15.6 -3.9 56499 1.4 799
78 09 29  15 15.3 -7.9 -2 14.9 -2.1 49346 1.3 759
78 09 29  16 14.1 -0.5 -2.9 13.8 -0.1 57732 0.5 730
78 09 29  17 12.6 14.7 -3.1 11.5 3.1 44351 1.7 722
78 09 29  18 11.2 74.3 0.6 2.9 10.4 68224 0.4 712
78 09 29  19 10.5 60.5 3.2 4 9.1 48082 0.2 706
78 09 29  20 10 54.7 3.9 4.2 8.1 56404 0.2 710
78 09 29  21 9.3 61.1 3.4 2.9 8.1 68824 0.2 694
78 09 29  22 8.6 64.4 2.6 2.7 7.8 44579 0.2 683
78 09 29  23 7.9 63.3 2 3 7.1 39760 0.2 661
78 09 30  0 7.3 59.8 2.3 2.8 6.3 NA NA NA
78 09 30  1 6.6 65.6 1.7 2.1 6 57382 0.5 664
78 09 30  2 6 70.8 1.3 1.4 5.5 63540 0.5 654
78 09 30  3 4.4 45.1 1 2.7 2.9 60856 2.5 635
78 09 30  4 3.6 -28 -1 -0.3 -0.6 80967 1.9 633
78 09 30  5 4 -47.6 -2.2 -0.1 -2.4 48391 1.2 642
78 09 30  6 4.1 -28.9 -3.1 -1.4 -1.9 45012 1.1 643
78 09 30  7 4.2 -42.7 -2.7 1.2 -2.7 45562 1.1 633
 and part of my code is:
Sys.setenv( TZ="GMT" )
dta<-read.table("IFEDIFIG1D",col.names=c("year", "month", "day",
"hour","B","LAT","BX","BZ","BY","SWT","SWD","SW"))
dta$year <- with( dta, ifelse(year < 50, year + 2000, year + 1900))
dta$datetime <- with( dta, as.POSIXct(ISOdatetime(year,
month,day,hour,0,0)))
x =  dta$datetime
B=dta$B
LAT=dta$LAT
BX=dta$BX
BZ=dta$BZ
 par(mfcol = c(3, 1), mar = numeric(4), oma = c(4, 4, 1, 1),
    mgp = c(2, 0.5, 0))#0.5 here controls x-axis margins
plot(x, B,type="l", axes = FALSE)
abline(v=-3)
axis(2L)
plot(x, LAT,type="l", axes = FALSE)
abline(v=-3)
axis(2L)
 plot(x, BX, type="l",axes = FALSE)
abline(v=-3)
axis(1L)
axis(2L)
mtext("A1", side = 1, outer = TRUE, line = 2.2)
mtext("B1", side = 2, outer = TRUE, line = 2.2,at =0.2)
mtext("B2", side = 2, outer = TRUE, line = 2.2,at =0.5)
mtext("B2", side = 2, outer = TRUE, line = 2.2,at =0.8)

If I do a simple plot of x and B, the x-axis will be fine, appearing as
Thu, Fri, Sat, Sun.
Please let me know what I am doing wrong with the multiple plot code above.
I want the same Thu, Fri, Sat, Sun to appear on the common x-axis.

I am most grateful for your kind response.

Warmest regards
Ogbos

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