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");
2018.02.14
$ temporalParse("14-02-2018","dd/MM/yyyy");
00d
$ temporalParse("14//02//2018","dd//MM//yyyy");
2018.02.14
$ temporalParse("14//02//2018","dd/MM/yyyy");
00d
$ temporalParse("14//02//2018","dd..MM..yyyy");
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");
2018.02.14
$ temporalParse("2018/2/6 02:33:01 PM","y/M/d h:m:s a");
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");
2018.02.02
$ temporalParse("02-FEB-2018","d-M-y");
00d
$ temporalParse("13:30:10.001","H:m:s.SSS");
13:30:10.001
$ temporalParse("13:30:10.001","H:m:s.S");
Invalid temporal format: 'H:m:s.S'. Millisecond (S) must have three digits.
$ temporalParse("13:30:10.008001","H:m:s.nnnnnn");
13:30:10.008001000
$ temporalParse("13:30:10.008001","H:m:s.n");
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");
2018.04.02
$ temporalParse("2-19-6","H-m-s");
02:19:06
$ temporalParse("002-019-006","H-m-s");
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");
2018.02.06T13:30:10.001
$ temporalParse("2018/2/6 13:30:10.01","y/M/d H:m:s.SSS");
00T
$ temporalParse("2018/2/6 13:30:10.000001","y/M/d H:m:s.nnnnnn");
2018.02.06T13:30:10.000001000
$ temporalParse("2018/2/6 13:30:10.0000010","y/M/d H:m:s.nnnnnn");
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");
14-02-2018
$ temporalFormat(2018.02.14,"dd/MMM/yy");
14/FEB/18
$ temporalFormat(02:19:06,"HH.mm.ss");
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");
2018.02.14
$ temporalParse("122506","MMddyy");
2006.12.25
$ temporalParse("155950","HHmmss");
15:59:50
$ temporalParse("035901PM","hhmmssaa");
15:59:01
$ temporalParse("02062018155956001000001","MMddyyyyHHmmssnnnnnnnnn");
2018.02.06T15:59:56.001000001