EVL

Date and Timestamp

Format string

Default formatting string:

timestamp: "%Y-%m-%d %H:%M:%S"  = "%F %T"  
date     : "%Y-%m-%d"           = "%F"

All possible format strings:

%%

a literal ‘%’

%a

locale’s abbreviated weekday name (e.g. ‘Sun’)

%A

locale’s full weekday name (e.g. ‘Sunday’)

%b

locale’s abbreviated month name (e.g. ‘Jan’)

%B

locale’s full month name (e.g. ‘January’)

%c

locale’s date and time (e.g. ‘Thu Mar 3 23:05:25 2005’)

%C

century; like ‘%Y’, except omit last two digits (e.g. ‘20’)

%d

day of month (e.g. ‘01’)

%D

date; same as ‘%m/%d/%y’

%e

day of month, space padded; same as ‘%_d’

%F

full date; same as ‘%Y-%m-%d’

%g

last two digits of year of ISO week number (see ‘%G’)

%G

year of ISO week number (see ‘%V’); normally useful only with ‘%V’

%h

same as ‘%b’

%H

hour (‘00’..‘23’)

%I

hour (‘01’..‘12’)

%j

day of year (‘001’..‘366’)

%k

hour, space padded (‘ 0’..‘23’); same as ‘%_H’

%l

hour, space padded (‘ 1’..‘12’); same as ‘%_I’

%m

month (‘01’..‘12’)

%M

minute (‘00’..‘59’)

%n

a newline

%p

locale’s equivalent of either ‘AM’ or ‘PM’; blank if not known

%P

like ‘%p’, but lower case

%r

locale’s 12-hour clock time (e.g. ‘11:11:04 PM’)

%R

24-hour hour and minute; same as ‘%H:%M’

%s

seconds since ‘1970-01-01 00:00:00 UTC’

%S

second (‘00’..‘60’)

%t

a tab

%T

time; same as ‘%H:%M:%S’

%u

day of week (‘1’..‘7’); ‘1’ is Monday

%U

week number of year, with Sunday as first day of week (‘00’..‘53’)

%V

ISO week number, with Monday as first day of week (‘01’..‘53’)

%w

day of week (‘0’..‘6’); ‘0’ is Sunday

%W

week number of year, with Monday as first day of week (‘00’..‘53’)

%x

locale’s date representation (e.g. ‘12/31/99’)

%X

locale’s time representation (e.g. ‘23:13:48’)

%y

last two digits of year (‘00’..‘99’)

%Y

year

By default, date pads numeric fields with zeroes. The following optional flags may follow ‘%’.

-

(hyphen) do not pad the field

_

(underscore) pad with spaces

0

(zero) pad with zeros

^

use upper case if possible

#

use opposite case if possible

EVD definition

Example of definition date and timestamp in evd file. The following dates data types definition are equivalent.

valid_from  date
valid_from  date("%F")
valid_from  date("%Y-%m-%d")

Following timestamps are all the same.

request_dt  timestamp
request_dt  timestamp("%F %T")
request_dt  timestamp("%Y-%m-%d %H:%M:%S")

Declaration in mapping

The following declarations are equivalent.

static timestamp min_date(1970,1,1,0,0,0);
static timestamp min_date("1970-01-01 00:00:00");
static timestamp min_date("1970-01-01 00:00:00", "%Y-%m-%d %H:%M:%S");
static timestamp min_date = timestamp::from_epoch_time(0);

static date min_date(1970,1,1);
static date min_date("1970-01-01");
static date min_date("1970-01-01", "%Y-%m-%d");

Manipulation, comparison

Lets have ‘timestamp ts(2017,5,31,19,37,0)’ and ‘date dt(2018,1,14)’ in the following examples.

Methods switching date and timestamp data type:

ts.to_date()

returns ‘2017-05-31’, i.e. cut off time and return date data type

dt.to_timestamp()

returns ‘2018-01-14 00:00:00’, i.e. add ‘00:00:00’ and return timestamp data type

Following methods return appropriate values as ‘int’.

ts.year()       -- 2017
dt.year()       -- 2018
ts.month()      -- 5
dt.month()      -- 1
ts.day()        -- 31
dt.day()        -- 14
ts.hour()       -- 19
ts.minute()     -- 37
ts.second()     -- 0
ts.epoch_time() -- 1496169420
ts.yearday()    -- 151
dt.yearday()    -- 14
ts.weekday()    -- 3 (Wednesday)
dt.weekday()    -- 0 (Sunday)

In the context of string, method ‘weekday()’ returns ‘sunday’, ...

‘weekday()’ returns ‘0’ for Sunday, ‘1’ for Monday, …, ‘6’ for Saturday.

These methods convert date and timestamp to string:

string str1 = ts.to_string();    // 2017-05-31 19:37:00,
                                 // i.e. uses default format string
string str2 = ts.to_string("%Y%m%d%H");     // 2017053119
string str3 = min_date.to_string("%Y%m%d"); // 19700101

Comparison: ‘==’, ‘!=’, ‘<’, ‘>’, ‘<=’, ‘>=’.

if (ts >= timestamp(1990,1,1) { ... }

Addition, subtraction:

ts += 65;          // add 65 seconds, i.e. 2017-05-31 19:38:05
ts--;              // 2017-05-31 19:38:04
date d(2017,5,31);
d -= 35;           // subtract 35 days, i.e. 2017-04-26

ts.add_year(1);    // 2018-05-31 19:38:04
d.add_month(-1);   // 2017-03-26
ts.add_day(6);     // 2018-06-06 19:38:04
ts.add_hour(-2);   // 2018-05-31 17:38:04
ts.add_minute(3);  // 2018-05-31 19:41:04
ts.add_second(-6); // 2018-05-31 19:37:58

The difference between ‘ts.add_second(10)’ and ‘ts+10’ is that in the first case we modify the object itself, but in the second case new value is returned. One can use then for example ‘ts.add_hour(2).add_minute(3)’.

Difference:

auto diff = ts - timestamp(2018,5,31,19,36,57); // 61 (seconds)
auto diff = d - date("2017-04-02");             // -6 (days)

Let’s summarize the logic:

date - int  => date          timestamp - int       => timestamp
date - date => int           timestamp - timestamp => int