Why is a “datetime” limited to 31 December, 3000?
EDIT: Updated code to show where the limits of the datetime datatype are set by the MQL 5 language.
void OnStart() // MQL5 Script Code { datetime dtNow = TimeCurrent(), dtMin = D'1970.01.01 00:00:00', dtMax = D'3000.12.31 23:59:59', dtLimit = dtMax + 8*60*60; Print( "Now Date: ", dtNow, " (", (long) dtNow, ")" ); Print( "Min Date: ", dtMin, " (", (long) dtMin, ")" ); Print( "Max Date: ", dtMax, " (", (long) dtMax, ")" ); Print( "Limit Date: ", dtLimit, " (", (long) dtLimit, ")" ); dtLimit++; Print( "Limit Date: ", dtLimit, " (", (long) dtLimit, ")" ); };Now Date: 2022.08.15 23:35:06 (1660606506) Min Date: 1970.01.01 00:00:00 (0) Max Date: 3000.12.31 23:59:59 (32535215999) Limit Date: 3001.01.01 07:59:59 (32535244799) Limit Date: wrong datetime (32535244800)
EDIT: Updated code to show where the limits of the datetime datatype are set by the MQL 5 language.
When googleing 32535244799 some interesting results come up.
One I found is here:
https://stackoverflow.com/questions/35048512/what-are-valid-arguments-for-localtime-function
As it seems, its not MQLs limitation, but MS Windows system function / return structure limitation.
https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/localtime-localtime32-localtime64?redirectedfrom=MSDN&view=msvc-170
- 2021.08.03
- TylerMSFT
- docs.microsoft.com
Dominik Christian Egert #: When googleing 32535244799 some interesting results come up. One I found is here: https://stackoverflow.com/questions/35048512/what-are-valid-arguments-for-localtime-function
As it seems, its not MQLs limitation, but MS Windows system function / return structure limitation. https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/localtime-localtime32-localtime64?redirectedfrom=MSDN&view=msvc-170Thank you @Dominik Christian Egert for your research. That was an interesting find.
From your references, it seems that it is not so much a limitation of the datetime (or _time64), but more a limitation of its conversion to and from a time structure or a string, for example by the _localtime or ctime functions.
But it is good to know that it is not a MQL limitation but an OS limitation not mentioned in the MQL documentation.
Also it seems, from what I have read so far, that each OS has defined their own limits on what constitutes a valid future timestamp and that the limit is not globally defined.
Now I am left wondering why Microsoft imposed such a limit?
Thank you @Dominik Christian Egert for your research. That was an interesting find.
From your references, it seems that it is not so much a limitation of the datetime (or _time64), but more a limitation of its conversion to and from a time structure or a string, for example by the _localtime or ctime functions.
But it is good to know that it is not a MQL limitation but an OS limitation not mentioned in the MQL documentation.
Also it seems, from what I have read so far, that each OS has defined their own limits on what constitutes a valid future timestamp and that the limit is not globally defined.
Now I am left wondering why Microsoft imposed such a limit?
Given that MetaQuotes does not even have a public issue or bug tracking system in place, like other software companies, I doubt they would even contemplate such a possibility.
However, it's puzzling that only a few trading software platforms actually have a public issue tracking system in place. I only know of one actually, namely MultiCharts.
- Free trading apps
- Over 8,000 signals for copying
- Economic news for exploring financial markets
You agree to website policy and terms of use
This is a question of curiosity. Why is a “datetime” limited to 31 December, 3000?
In the original MQL4, a “datetime” data-type was originally 4 bytes, presumably an “int” data-type with a limit of 2147483647 that would give a maximum date-time of D’2038.01.19 03:14:07’. Later on, with the appearance of MQL5 and update to MQL4+, the “datetime” datatype was updated to 8 bytes, presumably a “long” data-type with a limit of 9223372036854775807. However, according to the documentation, the date-time limit is 31 December, 3000. Its limit is probably D’3000.12.31 23:59:59’ or a value of 32535215999 seconds, which in hexadecimal would be 0x7933FFF7F and would occupy 4.5 bytes.
My question is — why limit it to 4.5 bytes, when it occupies 8 bytes? Is there a historical significance to this or compatibility with other languages?
Even if it is for allowing the “datetime” to be referenced in milliseconds and still fit in a “long”, it still does not make much sense. Even if we were to account for allowing for nanoseconds to fit in a “long”, this date limit would still fall short. Another possibility is for the value to be stored in a “double”, but that has 15 significant digits, which still allow for 4 extra digits, given that 32535215999 only has 11 digits.
So out of curiosity, does anyone know why MetaQuotes set this limitation on “datetime”?