Easter date is not constant. It changes
every year. For several years I had no idea on how to calculate the
Easter date in an year. If you could calculate when will be the
Easter fall on an year you can easily get a brief idea about another
related holidays like Palm Sunday, Maundy Thursday, Holy Saturday,
Good Friday, Easter Monday.
And finally do you want to have a glance of the code of ncal which is done in "C". Here is the link. All of us may be heard about Julian calendar and Gregorian calendar. But how many of us know the minute calculations based on that? Just figure how deep the rabbit hole goes!
In Christian calendar the date of
Easter has prime importance. The First Council of Nicaea established
the date of Easter as the first Sunday after the full moon following
the northern hemisphere's vernal equinox. According to the Catholic
church, the equinox is on 21 March, and the "Full Moon" is
not necessarily the astronomically correct date. The date of Easter
therefore varies between 22 March and 25 April. Eastern Christianity
bases its calculations on the Julian calendar whose 21 March
corresponds, during the 21st century, to 3 April in the Gregorian
calendar, in which the celebration of Easter therefore varies between
4 April and 8 May.
Sometime back I was checking the man
page of ncal. The man page says “The cal utility displays a simple
calendar in traditional format and ncal offers an alternative layout,
more options and the date of easter.” Yes, you can calculate the
easter day on AD 4012 now with this ncal utility. Just type the
following command in the GNU/Linux console.
ncal -e 4012
In the next moment, ncal will tell you
the result.
On 4012, Easter will be on 22 April
4012
And do you want to know when will be
the orthodox Easter on the same day? The command has a little
difference.
ncal -o 4012
The orthodox Easter on 4012 is on 6
May 4012
Want to look a weird calendar year according to the Gregorian system. Just look the calendar of 1752 calendar using cal command.
And just look on the month of September. Which day comes after September 2nd? Why? The answer will get from the man pages of cal. Type
That's the story of 1752 September. The smallest month in the Gregorian calendar system. But not all countries accepted Gregorian calendar system all of a sudden in one fine day. Some countries accepted it 1582, while some other countries accepted it centuries later. So how to find out when did Spain accepted Gregorian calendar system? Type the following command
In Turkey, the year 1926 was ended on December 18th! Cool, eh? In Greece they turned to Gregorian system on 1924 March. Lets try the following command
Want to look a weird calendar year according to the Gregorian system. Just look the calendar of 1752 calendar using cal command.
cal -y 1752
And just look on the month of September. Which day comes after September 2nd? Why? The answer will get from the man pages of cal. Type
man calMan page says "Assume the switch from Julian to Gregorian Calendar at the date associated with the country_code. If not specified, ncal tries to guess the switch date from the local environment or falls back to September 2, 1752. This was when Great Britain and her colonies switched to the Gregorian Calendar"
That's the story of 1752 September. The smallest month in the Gregorian calendar system. But not all countries accepted Gregorian calendar system all of a sudden in one fine day. Some countries accepted it 1582, while some other countries accepted it centuries later. So how to find out when did Spain accepted Gregorian calendar system? Type the following command
ncal -pHere is the result. Country code | Country name | Julian to Gregorian switch date.
AL Albania 1912-11-30 IT Italy 1582-10-04 AT Austria 1583-10-05 JP Japan 1918-12-18 AU Australia 1752-09-02 LI Lithuania 1918-02-01 BE Belgium 1582-12-14 LN Latin 9999-05-31 BG Bulgaria 1916-03-18 LU Luxembourg 1582-12-14 CA Canada 1752-09-02 LV Latvia 1918-02-01 CH Switzerland 1655-02-28 NL Netherlands 1582-12-14 CN China 1911-12-18 NO Norway 1700-02-18 CZ Czech Republic 1584-01-06 PL Poland 1582-10-04 DE Germany 1700-02-18 PT Portugal 1582-10-04 DK Denmark 1700-02-18 RO Romania 1919-03-31 ES Spain 1582-10-04 RU Russia 1918-01-31 FI Finland 1753-02-17 SI Slovenia 1919-03-04 FR France 1582-12-09 SE Sweden 1753-02-17 GB United Kingdom 1752-09-02 TR Turkey 1926-12-18 GR Greece 1924-03-09 *US United States 1752-09-02 HU Hungary 1587-10-21 YU Yugoslavia 1919-03-04 IS Iceland 1700-11-16China, Albania, Bulgaria, Russia, Lithuania, Latvia, Japan, Slovenia, Yugoslavia, Romania, Greece, Turkey (sorted chronologically) accepted Gregorian calendar in the 20th century. Turkey was the last republic adopted Gregorian calendar in this list. Ok. lets try to get the Turkey's official calendar on 1926. Type the command in the terminal.
ncal -s TR 1926
In Turkey, the year 1926 was ended on December 18th! Cool, eh? In Greece they turned to Gregorian system on 1924 March. Lets try the following command
ncal -s GR 3 1924And now let's see the 1924 March official calendar of Greece.
March 1924 Mo 4 24 31 Tu 5 25 We 6 26 Th 7 27 Fr 1 8 28 Sa 2 9 29 Su 3 23 30They lost two weeks in that March. Scary, no? And the most interesting calendar is 9999. I don't know what is the relevance of this. Lets check with two commands.
ncal -s LN 9999With this command we will get the normal calendar on that year.
ncal -s LN -j 9999With this command we can just figure how many days were in that year.
tom@debian:~$ ncal -s LN 9999
9999
January February March April
Mo 1 8 15 22 29 5 12 19 26 5 12 19 26 2 9 16 23 30
Tu 2 9 16 23 30 6 13 20 27 6 13 20 27 3 10 17 24
We 3 10 17 24 31 7 14 21 28 7 14 21 28 4 11 18 25
Th 4 11 18 25 1 8 15 22 1 8 15 22 29 5 12 19 26
Fr 5 12 19 26 2 9 16 23 2 9 16 23 30 6 13 20 27
Sa 6 13 20 27 3 10 17 24 3 10 17 24 31 7 14 21 28
Su 7 14 21 28 4 11 18 25 4 11 18 25 1 8 15 22 29
May June July August
Mo 7 14 21 28 16 23 30
Tu 1 8 15 22 29 17 24 31
We 2 9 16 23 30 18 25
Th 3 10 17 24 31 19 26
Fr 4 11 18 25 13 20 27
Sa 5 12 19 26 14 21 28
Su 6 13 20 27 15 22 29
September October November December
Mo 6 13 20 27 4 11 18 25 1 8 15 22 29 6 13 20 27
Tu 7 14 21 28 5 12 19 26 2 9 16 23 30 7 14 21 28
We 1 8 15 22 29 6 13 20 27 3 10 17 24 1 8 15 22 29
Th 2 9 16 23 30 7 14 21 28 4 11 18 25 2 9 16 23 30
Fr 3 10 17 24 1 8 15 22 29 5 12 19 26 3 10 17 24 31
Sa 4 11 18 25 2 9 16 23 30 6 13 20 27 4 11 18 25
Su 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26
tom@debian:~$ ncal -s LN -j 9999
9999
January February March
Mo 1 8 15 22 29 36 43 50 57 64 71 78 85
Tu 2 9 16 23 30 37 44 51 58 65 72 79 86
We 3 10 17 24 31 38 45 52 59 66 73 80 87
Th 4 11 18 25 32 39 46 53 60 67 74 81 88
Fr 5 12 19 26 33 40 47 54 61 68 75 82 89
Sa 6 13 20 27 34 41 48 55 62 69 76 83 90
Su 7 14 21 28 35 42 49 56 63 70 77 84
April May June
Mo 92 99 106 113 120 127 134 141 148
Tu 93 100 107 114 121 128 135 142 149
We 94 101 108 115 122 129 136 143 150
Th 95 102 109 116 123 130 137 144 151
Fr 96 103 110 117 124 131 138 145
Sa 97 104 111 118 125 132 139 146
Su 91 98 105 112 119 126 133 140 147
July August September
Mo 155 162 169 176 183 190 197
Tu 156 163 170 177 184 191 198
We 157 164 171 178 185 192 199
Th 158 165 172 179 186 193 200
Fr 152 159 166 173 180 187 194
Sa 153 160 167 174 181 188 195
Su 154 161 168 175 182 189 196
October November December
Mo 204 211 218 225 232 239 246 253 260 267 274 281 288
Tu 205 212 219 226 233 240 247 254 261 268 275 282 289
We 206 213 220 227 234 241 248 255 262 269 276 283 290
Th 207 214 221 228 235 242 249 256 263 270 277 284 291
Fr 201 208 215 222 229 236 243 250 257 264 271 278 285 292
Sa 202 209 216 223 230 237 244 251 258 265 272 279 286
Su 203 210 217 224 231 238 245 252 259 266 273 280 287
So there is only 292 days in that year, 73 days will be lost. June, July months are not in the picture. And 12 days of August also missing. People who follow Latin Calendar goes to sleep on 9999 March 31 will be woke up on August 13! Anyway, I still do not have any idea about the Latin Calendar system. I think this calendar is the Julian calendar. But who follows it still, why does it switch on 9999 March 31 to Gregorian system? Maybe, Julian calendar will be abandoned on 9999 March 31. I searched lots of web pages regarding this, but from nowhere I got satisfactory results.And finally do you want to have a glance of the code of ncal which is done in "C". Here is the link. All of us may be heard about Julian calendar and Gregorian calendar. But how many of us know the minute calculations based on that? Just figure how deep the rabbit hole goes!
6 comments:
Quite interesting. I heard about the Julian calendar and Gregorian calendar, but was not aware about the differences between them. Not familiar with commandline, but even tried it and the experience was so wonderful. The post is really useful. Thanks for that.
Very Informative. Good effort
Thank you spotblog. Thanks saju george. So happy that you read it. Planning to post something more deep about ncal and Gregorian calendar.
Hackingtom, its no problem if they abandon the Julian calendar on 9999 March 31st. Me and you and the entire people live today will no longer exist on that day, so why should we bother about that:-) And I think the Julian calendar is still used by some eastern orthodox churches to calculate their easter dates. But I am not sure. Anyway this post will help the unix command newbies to find the wonders behind that pretty small utility - cal and ncal.
Just want to say something more. I got the exact result what you could not get from the web. The Julian calendar still used by the Orthodox church in Russia. That's why ncal still gives the option -s LN. In the Julian calendar, the tropical year is approximated as 365¼ days = 365.25 days. This gives an error of 1 day in approximately 128 years. The approximation 365¼ is achieved by having 1 leap year every 4 years.Read more @ http://www.tondering.dk/claus/cal/julian.php
snapakyohan, thanks for the info. I guessed that the Julian calendar is being used by some orthodox churches. So I think when we use ncal with -o option it searches for the Julian calendar. Anyway thanks for the link.
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