Parsing and Format of Temporal Variables
DolphinDB provides a function temporalParse to convert a string with specified format to DolphinDB temporal variable, and function temporalFormat to convert a DolphinDB temporal variable to a string with specified format.
The following table shows the temporal formats in DolphinDB:
Format | Explanation | Range of value |
---|---|---|
yyyy | year (4 digits) | 1000-9999 |
yy | year (2 digits) | 00-99. (00-39: 2000-2039; 40-99: 1940-1999) |
MM | month in year | 1-12 |
MMM | month in year | JAN, FEB, ... DEC (case insensitive) |
dd | day in month | 1-31 |
HH | hour in day | 0-23 |
hh | hour in AM/PM | 0-11 |
mm | minute in hour | 0-59 |
ss | second in minute | 0-59 |
aa | AM/PM marker | AM, PM. (case-insensitive) |
SSS | millisecond | 0-999 |
nnnnnn | microsecond | 0-999999 |
nnnnnnnnn | nanosecond | 0-999999999 |
The parameter format in function temporalParse
and
temporalFormat
has 2 types of representation:
-
With deliminator(s)
Any symbol or character is treated as a deliminator except the characters that are used to express a temporal format: y, M, d, H, h, m, s, a, S, and n. A deliminator in the parameter format should be identical as the deliminator in the input string.
temporalParse("14-02-2018","dd-MM-yyyy");
// output
2018.02.14
temporalParse("14-02-2018","dd/MM/yyyy");
// output
00d
temporalParse("14//02//2018","dd//MM//yyyy");
// output
2018.02.14
temporalParse("14//02//2018","dd/MM/yyyy");
// output
00d
temporalParse("14//02//2018","dd..MM..yyyy");
// output
00d
We can simplify the formats by using a single letter between deliminators for the parameter format. For example, we can use the format "y/M/d" instead of "yyyy/MM/dd" for "2018/01/16". As "y" may mean both "yyyy" and "yy", for this case the system decides on the format based on the number of digits between deliminators.
temporalParse("14-02-18","d-M-y");
// output
2018.02.14
temporalParse("2018/2/6 02:33:01 PM","y/M/d h:m:s a");
// output
2018.02.06T14:33:01
"MMM","SSS", "nnnnnn" and "nnnnnnnnn", however, cannot be simplified to a single letter.
temporalParse("02-FEB-2018","d-MMM-y");
// output
2018.02.02
temporalParse("02-FEB-2018","d-M-y");
// output
00d
temporalParse("13:30:10.001","H:m:s.SSS");
// output
13:30:10.001
temporalParse("13:30:10.001","H:m:s.S");
// output
Invalid temporal format: 'H:m:s.S'. Millisecond (S) must have three digits.
temporalParse("13:30:10.008001","H:m:s.nnnnnn");
// output
13:30:10.008001000
temporalParse("13:30:10.008001","H:m:s.n");
// output
Invalid temporal format: 'H:m:s.n'. Nanosecond (n) must have six or nine digits.
The temporalParse
function is very flexible in interpreting the numbers
between deliminators in the input string.
temporalParse("2-4-18","d-M-y");
// output
2018.04.02
temporalParse("2-19-6","H-m-s");
// output
02:19:06
temporalParse("002-019-006","H-m-s");
// output
02:19:06
For millisecond, microsecond and nanosecond, however, the corresponding number of digits in the input string must be 3, 6 and 9 respectively.
temporalParse("2018/2/6 13:30:10.001","y/M/d H:m:s.SSS");
// output
2018.02.06T13:30:10.001
temporalParse("2018/2/6 13:30:10.01","y/M/d H:m:s.SSS");
// output
00T
temporalParse("2018/2/6 13:30:10.000001","y/M/d H:m:s.nnnnnn");
// output
2018.02.06T13:30:10.000001000
temporalParse("2018/2/6 13:30:10.0000010","y/M/d H:m:s.nnnnnn");
// output
00N
In comparision, for function temporalFormat
, the number of characters
between deliminators determines the number of digits in the output.
temporalFormat(2018.02.14,"dd-MM-yyyy");
// output
14-02-2018
temporalFormat(2018.02.14,"dd/MMM/yy");
// output
14/FEB/18
temporalFormat(02:19:06,"HH.mm.ss");
// output
02.19.06
-
Without deliminators
For this reprensentation, the parameter format must be composed of the formats in the temporal formats table. We cannot use a single letter to represent a format in the temporal format table.
temporalParse("20180214","yyyyMMdd");
// output
2018.02.14
temporalParse("122506","MMddyy");
// output
2006.12.25
temporalParse("155950","HHmmss");
// output
15:59:50
temporalParse("035901PM","hhmmssaa");
// output
15:59:01
temporalParse("02062018155956001000001","MMddyyyyHHmmssnnnnnnnnn");
// output
2018.02.06T15:59:56.001000001