Almost every serious programming language has to deal with database access, if not out of love, then at least out of practical necessity.

The theoretical background of a functional programming language is somewhat hostile to this, because pure functional langauges tend to dislike state and a database has the exact purpose to preserve state for a long time. Treating the database as somewhat external and describing its access with monads will at least please theoretical purists to some extent.

In case of Scala things are not so strict, it is allowed to leave the purely functional path where adequate. But there are reasons to follow it and to leave it only in well defined, well known, well understood and well contained exceptions… So the database itself may be acceptable.

Another intellectual and practical challenge is the fact that modern Scala architectures like to be reactive, like to uncouple things, become asynchronous. This is possible with databases, but it is very unusual for database drivers to support this. And it is actually quite contrary to the philosophy of database transactions. It can be addressed with future database drivers, but I do not expect this to be easy to use properly in conjunction with transactions.

It is worthwhile to think about
immutability and databases.
For now we can assume that the database is there and can be used.

So the question is, why not integrate existing and established persistence frameworks like JPA, Hibernate, Eclipslink and other OR-mapping-based systems into Scala, with Scala language binding?

Actually I am quite happy they did not go this path. Hibernate is broken and buggy, but the generic concept behind it is broken in my opinion. I do not think that it is theoretically correct, especially if we should program with waterproof transactions and actually defeat them by JPA-caching without even being aware of it? But for practical purposes, I actually doubt that taming JPA for non trivial applications is really easier than good old JDBC.

Anyway, Scala took the approach of building something in the lines of JDBC, but making it nicer. It is called Slick, currently Slick 3. Some links:
* Slick
* Slick 3.1.1
* Documentation
* Github
* Assynchronous DB access
* Recording of the Slick Workshop at ScalaX

What Slick basically does is building queries using Scala language. It does pack the results into Scala structures. Important is, that the DB is not hidden. So we just do the same as with JDBC, but in a more advanced way.

This article is inspired by my visit to Scala X.

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How to create ISO Date String

It is a more and more common task that we need to have a date or maybe date with time as String.

There are two reasonable ways to do this:
* We may want the date formatted in the users Locale, whatever that is.
* We want to use a generic date format, that is for a broader audience or for usage in data exchange formats, log files etc.

The first issue is interesting, because it is not always trivial to teach the software to get the right locale and to use it properly… The mechanisms are there and they are often used correctly, but more often this is just working fine for the locale that the software developers where asked to support.

So now the question is, how do we get the ISO-date of today in different environments.

Linux/Unix-Shell (bash, tcsh, …)

date "+%F"


\def\dayiso{\ifcase\day \or
01\or 02\or 03\or 04\or 05\or 06\or 07\or 08\or 09\or 10\or% 1..10
11\or 12\or 13\or 14\or 15\or 16\or 17\or 18\or 19\or 20\or% 11..20
21\or 22\or 23\or 24\or 25\or 26\or 27\or 28\or 29\or 30\or% 21..30
\def\monthiso{\ifcase\month \or
01\or 02\or 03\or 04\or 05\or 06\or 07\or 08\or 09\or 10\or 11\or 12\fi}

This can go into a file isodate.sty which can then be included by \include or \input Then using \todayiso in your TeX document will use the current date. To be more precise, it is the date when TeX or LaTeX is called to process the file. This is what I use for my paper letters.


(From Fritz Zaucker, see his comment below):

\usepackage{isodate} % load package
\isodate % switch to ISO format
\today % print date according to current format



On Oracle Docs this function is documented.
It can be chosen as a default using ALTER SESSION for the whole session. Or in SQL-developer it can be configured. Then it is ok to just call


Btw. Oracle allows to add numbers to dates. These are days. Use fractions of a day to add hours or minutes.


(From Fritz Zaucker, see his comment):

select current_date;
—> 2016-01-08

select now();
—> 2016-01-08 14:37:55.701079+01


In Emacs I like to have the current Date immediately:

(defun insert-current-date ()
"inserts the current date"
(let ((x (current-time-string)))
(concat (substring x 20 24)
(cdr (assoc (substring x 4 7)
(let ((y (substring x 8 9)))
(if (string= y " ") "0" y))
(substring x 9 10)))))
(global-set-key [S-f5] 'insert-current-date)

Pressing Shift-F5 will put the current date into the cursor position, mostly as if it had been typed.

Emacs (better Variant)

(From Thomas, see his comment below):

(defun insert-current-date ()
"Insert current date."
(insert (format-time-string "%Y-%m-%d")))


In Perl we can use a command line call

perl -e 'use POSIX qw/strftime/;print strftime("%F", localtime()), "\n"'

or to use it in larger programms

use POSIX qw/strftime/;
my $isodate_of_today = strftime("%F", localtime());

I am not sure, if this works on MS-Windows as well, but Linux-, Unix- and MacOS-X-users should see this working.

If someone has tried it on Windows, I will be interested to hear about it…
Maybe I will try it out myself…

Perl 5 (second suggestion)

(From Fritz Zaucker, see his comment below):

perl -e 'use DateTime; use 5.10.0; say DateTime->now->strftime(„%F“);‘

Perl 6

(From Fritz Zaucker, see his comment below):




This is even more elegant than Perl:

ruby -e 'puts"%F")'

will do it on the command line.
Or if you like to use it in your Ruby program, just use

d =
s = d.strftime("%F")

Btw. like in Oracle SQL it is possible add numbers to this. In case of Ruby, you are adding seconds.

It is slightly confusing that Ruby has two different types, Date and Time. Not quite as confusing as Java, but still…
Time is ok for this purpose.

C on Linux / Posix / Unix


main(int argc, char **argv) {

char s[12];
time_t seconds_since_1970 = time(NULL);
struct tm local;
struct tm gmt;
localtime_r(&seconds_since_1970, &local);
gmtime_r(&seconds_since_1970, &gmt);
size_t l1 = strftime(s, 11, "%Y-%m-%d", &local);
printf("local:\t%s\n", s);
size_t l2 = strftime(s, 11, "%Y-%m-%d", &gmt);
printf("gmt:\t%s\n", s);

This speeks for itself..
But if you like to know: time() gets the seconds since 1970 as some kind of integer.
localtime_r or gmtime_r convert it into a structur, that has seconds, minutes etc as separate fields.
stftime formats it. Depending on your C it is also possible to use %F.


import java.util.Date
import java.text.SimpleDateFormat
val s : String = new SimpleDateFormat("YYYY-MM-dd").format(new Date())

This uses the ugly Java-7-libraries. We want to go to Java 8 or use Joda time and a wrapper for Scala.

Java 7

import java.util.Date
import java.text.SimpleDateFormat

String s = new SimpleDateFormat("YYYY-MM-dd").format(new Date());

Please observe that SimpleDateFormat is not thread safe. So do one of the following:
* initialize it each time with new
* make sure you run only single threaded, forever
* use EJB and have the format as instance variable in a stateless session bean
* protect it with synchronized
* protect it with locks
* make it a thread local variable

In Java 8 or Java 7 with Joda time this is better. And the toString()-method should have ISO8601 as default, but off course including the time part.


This is quite easy to achieve in many environments.
I could provide more, but maybe I leave this to you in the comments section.
What could be interesting:
* better ways for the ones that I have provided
* other databases
* other editors (vim, sublime, eclipse, idea,…)
* Office packages (Libreoffice and MS-Office)
* C#
* F#
* Clojure
* C on MS-Windows
* Perl and Ruby on MS-Windows
* Java 8
* Scala using better libraries than the Java-7-library for this
* Java using better libraries than the Java-7-library for this
* C++
* Python
* Cobol
* JavaScript
* …
If you provide a reasonable solution I will make it part of the article with a reference…
See also Date Formats

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