  *
  * Should be good estimation for -30°C <= T <= 70°C
  */
-int8_t dew_point[41][21] = {
-           /* 0.5%  5%   10%  15%  20%  25%  30%  35%  40%  45%  50%  55%  60%  65%  70%  75%  80%  85%  90%  95% 100%*/
-/*  50°C */  {-26,   1,  11,  17,  21,  25,  28,  31,  33,  35,  37,  39,  40,  42,  43,  44,  46,  47,  48,  49,  50},
-/*  48°C */  {-27,   0,  10,  16,  21,  24,  27,  30,  32,  34,  36,  38,  39,  41,  42,  43,  45,  46,  47,  48,  48},
-/*  46°C */  {-28,   0,   9,  15,  20,  23,  26,  29,  31,  33,  35,  37,  38,  40,  41,  43,  44,  45,  46,  46,  46},
-/*  44°C */  {-29,  -3,   6,  12,  16,  20,  23,  25,  28,  30,  31,  33,  35,  36,  37,  39,  40,  41,  42,  43,  44},
-/*  42°C */  {-31,  -5,   5,  10,  15,  18,  21,  24,  26,  28,  30,  31,  33,  34,  35,  37,  38,  39,  40,  41,  42},
-/*  40°C */  {-32,  -6,   3,   9,  13,  16,  19,  22,  24,  26,  28,  29,  31,  32,  34,  35,  36,  37,  38,  39,  40},
-/*  38°C */  {-33,  -8,   1,   7,  11,  15,  18,  20,  22,  24,  26,  27,  29,  30,  32,  33,  34,  35,  36,  37,  38},
-/*  36°C */  {-34,  -9,   0,   6,  10,  13,  16,  18,  20,  22,  24,  26,  27,  28,  30,  31,  32,  33,  34,  35,  36},
-/*  34°C */  {-35, -11,  -2,   4,   8,  11,  14,  16,  19,  20,  22,  24,  25,  27,  28,  29,  30,  31,  32,  33,  34},
-/*  32°C */  {-36, -12,  -3,   2,   6,  10,  12,  15,  17,  19,  20,  22,  23,  25,  26,  27,  28,  29,  30,  31,  32},
-/*  30°C */  {-37, -13,  -5,   1,   5,   8,  11,  13,  15,  17,  18,  20,  21,  23,  24,  25,  26,  27,  28,  29,  30},
-/*  28°C */  {-38, -15,  -6,  -1,   3,   6,   9,  11,  13,  15,  17,  18,  20,  21,  22,  23,  24,  25,  26,  27,  28},
-/*  26°C */  {-40, -16,  -8,  -3,   1,   4,   7,   9,  11,  13,  15,  16,  18,  19,  20,  21,  22,  23,  24,  25,  26},
-/*  24°C */  {-41, -18,  -9,  -4,   0,   3,   5,   8,  10,  11,  13,  14,  16,  17,  18,  19,  20,  21,  22,  23,  24},
-/*  22°C */  {-42, -19, -11,  -6,  -2,   1,   4,   6,   8,   9,  11,  13,  14,  15,  16,  17,  18,  19,  20,  21,  22},
-/*  20°C */  {-43, -21, -13,  -7,  -4,  -1,   2,   4,   6,   8,   9,  11,  12,  13,  14,  15,  16,  17,  18,  19,  20},
-/*  18°C */  {-44, -22, -14,  -9,  -5,  -2,   0,   2,   4,   6,   7,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18},
-/*  16°C */  {-45, -23, -16, -11,  -7,  -4,  -2,   0,   2,   4,   6,   7,   8,   9,  10,  12,  13,  13,  14,  15,  16},
-/*  14°C */  {-46, -25, -17, -12,  -9,  -6,  -3,  -1,   1,   2,   4,   5,   6,   7,   9,  10,  11,  11,  12,  13,  14},
-/*  12°C */  {-47, -26, -19, -14, -10,  -8,  -5,  -3,  -1,   0,   2,   3,   4,   6,   7,   8,   9,  10,  10,  11,  12},
-/*  10°C */  {-49, -28, -20, -16, -12,  -9,  -7,  -5,  -3,  -1,   0,   1,   3,   4,   5,   6,   7,   8,   8,   9,  10},
-/*   8°C */  {-50, -29, -22, -17, -14, -11,  -9,  -7,  -5,  -3,  -2,  -1,   1,   2,   3,   4,   5,   6,   6,   7,   8},
-/*   6°C */  {-51, -31, -23, -19, -15, -13, -10,  -8,  -7,  -5,  -4,  -2,  -1,   0,   1,   2,   3,   4,   4,   5,   6},
-/*   4°C */  {-52, -32, -25, -20, -17, -14, -12, -10,  -9,  -7,  -6,  -4,  -3,  -2,  -1,   0,   1,   2,   2,   3,   4},
-/*   2°C */  {-53, -34, -26, -22, -19, -16, -14, -12, -10,  -9,  -7,  -6,  -5,  -4,  -3,  -2,  -1,   0,   1,   1,   2},
-/*   0°C */  {-54, -35, -28, -24, -20, -18, -16, -14, -12, -11,  -9,  -8,  -7,  -6,  -5,  -4,  -3,  -2,  -1,  -1,   0},
-/*  -2°C */  {-55, -36, -30, -25, -22, -20, -17, -16, -14, -12, -11, -10,  -9,  -8,  -7,  -6,  -5,  -4,  -3,  -3,  -2},
-/*  -4°C */  {-57, -38, -31, -27, -24, -21, -19, -17, -16, -14, -13, -12, -11, -10,  -9,  -8,  -7,  -6,  -5,  -5,  -4},
-/*  -6°C */  {-58, -39, -33, -29, -25, -23, -21, -19, -18, -16, -15, -14, -13, -12, -11, -10,  -9,  -8,  -7,  -7,  -6},
-/*  -8°C */  {-59, -41, -34, -30, -27, -25, -23, -21, -19, -18, -17, -16, -14, -13, -13, -12, -11, -10,  -9,  -9,  -8},
-/* -10°C */  {-60, -42, -36, -32, -29, -26, -24, -23, -21, -20, -19, -17, -16, -15, -14, -14, -13, -12, -11, -11, -10},
-/* -12°C */  {-61, -44, -37, -33, -30, -28, -26, -24, -23, -22, -20, -19, -18, -17, -16, -16, -15, -14, -13, -13, -12},
-/* -14°C */  {-62, -45, -39, -35, -32, -30, -28, -26, -25, -23, -22, -21, -20, -19, -18, -18, -17, -16, -15, -15, -14},
-/* -16°C */  {-63, -46, -40, -37, -34, -32, -30, -28, -27, -25, -24, -23, -22, -21, -20, -19, -19, -18, -17, -17, -16},
-/* -18°C */  {-64, -48, -42, -38, -35, -33, -31, -30, -28, -27, -26, -25, -24, -23, -22, -21, -21, -20, -19, -19, -18},
-/* -20°C */  {-66, -49, -44, -40, -37, -35, -33, -32, -30, -29, -28, -27, -26, -25, -24, -23, -23, -22, -21, -21, -20},
-/* -22°C */  {-67, -51, -45, -41, -39, -37, -35, -33, -32, -31, -30, -29, -28, -27, -26, -25, -25, -24, -23, -23, -22},
-/* -24°C */  {-68, -52, -47, -43, -40, -38, -37, -35, -34, -33, -32, -31, -30, -29, -28, -27, -26, -26, -25, -25, -24},
-/* -26°C */  {-69, -54, -48, -45, -42, -40, -38, -37, -36, -34, -33, -32, -31, -31, -30, -29, -28, -28, -27, -27, -26},
-/* -28°C */  {-70, -55, -50, -46, -44, -42, -40, -39, -37, -36, -35, -34, -33, -33, -32, -31, -30, -30, -29, -29, -28},
-/* -30°C */  {-71, -57, -51, -48, -45, -44, -42, -40, -39, -38, -37, -36, -35, -34, -34, -33, -32, -32, -31, -31, -30}};
+//int8_t dew_point[41][21] = {
+//           /* 0.5%  5%   10%  15%  20%  25%  30%  35%  40%  45%  50%  55%  60%  65%  70%  75%  80%  85%  90%  95% 100%*/
+///*  50°C */  {-26,   1,  11,  17,  21,  25,  28,  31,  33,  35,  37,  39,  40,  42,  43,  44,  46,  47,  48,  49,  50},
+///*  48°C */  {-27,   0,  10,  16,  21,  24,  27,  30,  32,  34,  36,  38,  39,  41,  42,  43,  45,  46,  47,  48,  48},
+///*  46°C */  {-28,   0,   9,  15,  20,  23,  26,  29,  31,  33,  35,  37,  38,  40,  41,  43,  44,  45,  46,  46,  46},
+///*  44°C */  {-29,  -3,   6,  12,  16,  20,  23,  25,  28,  30,  31,  33,  35,  36,  37,  39,  40,  41,  42,  43,  44},
+///*  42°C */  {-31,  -5,   5,  10,  15,  18,  21,  24,  26,  28,  30,  31,  33,  34,  35,  37,  38,  39,  40,  41,  42},
+///*  40°C */  {-32,  -6,   3,   9,  13,  16,  19,  22,  24,  26,  28,  29,  31,  32,  34,  35,  36,  37,  38,  39,  40},
+///*  38°C */  {-33,  -8,   1,   7,  11,  15,  18,  20,  22,  24,  26,  27,  29,  30,  32,  33,  34,  35,  36,  37,  38},
+///*  36°C */  {-34,  -9,   0,   6,  10,  13,  16,  18,  20,  22,  24,  26,  27,  28,  30,  31,  32,  33,  34,  35,  36},
+///*  34°C */  {-35, -11,  -2,   4,   8,  11,  14,  16,  19,  20,  22,  24,  25,  27,  28,  29,  30,  31,  32,  33,  34},
+///*  32°C */  {-36, -12,  -3,   2,   6,  10,  12,  15,  17,  19,  20,  22,  23,  25,  26,  27,  28,  29,  30,  31,  32},
+///*  30°C */  {-37, -13,  -5,   1,   5,   8,  11,  13,  15,  17,  18,  20,  21,  23,  24,  25,  26,  27,  28,  29,  30},
+///*  28°C */  {-38, -15,  -6,  -1,   3,   6,   9,  11,  13,  15,  17,  18,  20,  21,  22,  23,  24,  25,  26,  27,  28},
+///*  26°C */  {-40, -16,  -8,  -3,   1,   4,   7,   9,  11,  13,  15,  16,  18,  19,  20,  21,  22,  23,  24,  25,  26},
+///*  24°C */  {-41, -18,  -9,  -4,   0,   3,   5,   8,  10,  11,  13,  14,  16,  17,  18,  19,  20,  21,  22,  23,  24},
+///*  22°C */  {-42, -19, -11,  -6,  -2,   1,   4,   6,   8,   9,  11,  13,  14,  15,  16,  17,  18,  19,  20,  21,  22},
+///*  20°C */  {-43, -21, -13,  -7,  -4,  -1,   2,   4,   6,   8,   9,  11,  12,  13,  14,  15,  16,  17,  18,  19,  20},
+///*  18°C */  {-44, -22, -14,  -9,  -5,  -2,   0,   2,   4,   6,   7,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18},
+///*  16°C */  {-45, -23, -16, -11,  -7,  -4,  -2,   0,   2,   4,   6,   7,   8,   9,  10,  12,  13,  13,  14,  15,  16},
+///*  14°C */  {-46, -25, -17, -12,  -9,  -6,  -3,  -1,   1,   2,   4,   5,   6,   7,   9,  10,  11,  11,  12,  13,  14},
+///*  12°C */  {-47, -26, -19, -14, -10,  -8,  -5,  -3,  -1,   0,   2,   3,   4,   6,   7,   8,   9,  10,  10,  11,  12},
+///*  10°C */  {-49, -28, -20, -16, -12,  -9,  -7,  -5,  -3,  -1,   0,   1,   3,   4,   5,   6,   7,   8,   8,   9,  10},
+///*   8°C */  {-50, -29, -22, -17, -14, -11,  -9,  -7,  -5,  -3,  -2,  -1,   1,   2,   3,   4,   5,   6,   6,   7,   8},
+///*   6°C */  {-51, -31, -23, -19, -15, -13, -10,  -8,  -7,  -5,  -4,  -2,  -1,   0,   1,   2,   3,   4,   4,   5,   6},
+///*   4°C */  {-52, -32, -25, -20, -17, -14, -12, -10,  -9,  -7,  -6,  -4,  -3,  -2,  -1,   0,   1,   2,   2,   3,   4},
+///*   2°C */  {-53, -34, -26, -22, -19, -16, -14, -12, -10,  -9,  -7,  -6,  -5,  -4,  -3,  -2,  -1,   0,   1,   1,   2},
+///*   0°C */  {-54, -35, -28, -24, -20, -18, -16, -14, -12, -11,  -9,  -8,  -7,  -6,  -5,  -4,  -3,  -2,  -1,  -1,   0},
+///*  -2°C */  {-55, -36, -30, -25, -22, -20, -17, -16, -14, -12, -11, -10,  -9,  -8,  -7,  -6,  -5,  -4,  -3,  -3,  -2},
+///*  -4°C */  {-57, -38, -31, -27, -24, -21, -19, -17, -16, -14, -13, -12, -11, -10,  -9,  -8,  -7,  -6,  -5,  -5,  -4},
+///*  -6°C */  {-58, -39, -33, -29, -25, -23, -21, -19, -18, -16, -15, -14, -13, -12, -11, -10,  -9,  -8,  -7,  -7,  -6},
+///*  -8°C */  {-59, -41, -34, -30, -27, -25, -23, -21, -19, -18, -17, -16, -14, -13, -13, -12, -11, -10,  -9,  -9,  -8},
+///* -10°C */  {-60, -42, -36, -32, -29, -26, -24, -23, -21, -20, -19, -17, -16, -15, -14, -14, -13, -12, -11, -11, -10},
+///* -12°C */  {-61, -44, -37, -33, -30, -28, -26, -24, -23, -22, -20, -19, -18, -17, -16, -16, -15, -14, -13, -13, -12},
+///* -14°C */  {-62, -45, -39, -35, -32, -30, -28, -26, -25, -23, -22, -21, -20, -19, -18, -18, -17, -16, -15, -15, -14},
+///* -16°C */  {-63, -46, -40, -37, -34, -32, -30, -28, -27, -25, -24, -23, -22, -21, -20, -19, -19, -18, -17, -17, -16},
+///* -18°C */  {-64, -48, -42, -38, -35, -33, -31, -30, -28, -27, -26, -25, -24, -23, -22, -21, -21, -20, -19, -19, -18},
+///* -20°C */  {-66, -49, -44, -40, -37, -35, -33, -32, -30, -29, -28, -27, -26, -25, -24, -23, -23, -22, -21, -21, -20},
+///* -22°C */  {-67, -51, -45, -41, -39, -37, -35, -33, -32, -31, -30, -29, -28, -27, -26, -25, -25, -24, -23, -23, -22},
+///* -24°C */  {-68, -52, -47, -43, -40, -38, -37, -35, -34, -33, -32, -31, -30, -29, -28, -27, -26, -26, -25, -25, -24},
+///* -26°C */  {-69, -54, -48, -45, -42, -40, -38, -37, -36, -34, -33, -32, -31, -31, -30, -29, -28, -28, -27, -27, -26},
+///* -28°C */  {-70, -55, -50, -46, -44, -42, -40, -39, -37, -36, -35, -34, -33, -33, -32, -31, -30, -30, -29, -29, -28},
+///* -30°C */  {-71, -57, -51, -48, -45, -44, -42, -40, -39, -38, -37, -36, -35, -34, -34, -33, -32, -32, -31, -31, -30}};
 
 
 /*

    if (temp < -31.0 || temp > 50)
        return 100; // treat it as an error.

    int temp_idx = 40 - (temp + 30.0)/2;
    if (temp_idx < 0) temp_idx = 0;
    if (temp_idx > 40) temp_idx = 40;

    time_format[1] = ret % 10 + ('0');

    if (ret != 0 && !full_update)
       goto end;

    // Update all date string - very little optimization gain

