SOURCE_DATE_EPOCH: add missing syntax highlighting

### Python >= 3.x

```

```python

import os

import time

import datetime

… or with fewer imports and rendering to a string:

```

```python

import os

import time

If you still require Python 2.x support, you will need to use the non-recommended [`datetime.utcfromtimestamp`](https://docs.python.org/3.8/library/datetime.html#datetime.datetime.utcfromtimestamp) method ([more info](https://blog.ganssle.io/articles/2019/11/utcnow.html)):

```

```python

import os

import time

import datetime

For GNU systems:

```

```bash

BUILD_DATE="$(date --utc --date="@${SOURCE_DATE_EPOCH:-$(date +%s)}" +%Y-%m-%d)"

```

If you need to support BSD date as well you should fallback to trying ther `-r seconds` timestamp variant:

```

```bash

DATE_FMT="+%Y-%m-%d"

SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(date +%s)}"

BUILD_DATE=$(date -u -d "@$SOURCE_DATE_EPOCH" "$DATE_FMT" 2>/dev/null || date -u -r "$SOURCE_DATE_EPOCH" "$DATE_FMT" 2>/dev/null || date -u "$DATE_FMT")

### Perl

```

```perl

use POSIX qw(strftime);

my $date = strftime("%Y-%m-%d", gmtime($ENV{SOURCE_DATE_EPOCH} || time));

```

### Makefile

```

```make

DATE_FMT = +%Y-%m-%d

ifdef SOURCE_DATE_EPOCH

    BUILD_DATE ?= $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || date -u "$(DATE_FMT)")

### CMake

```

```cmake

STRING(TIMESTAMP BUILD_DATE "%Y-%m-%d" UTC)

```

If you would like to support legacy/archival versions of CMake, you can use this less-preferred variant:

```

```cmake

if (DEFINED ENV{SOURCE_DATE_EPOCH})

  execute_process(

    COMMAND "date" "-u" "-d" "@$ENV{SOURCE_DATE_EPOCH}" "+%Y-%m-%d"

By deliberate design, [Meson does not provide access to environment variables in build files](https://github.com/mesonbuild/meson/issues/9#issuecomment-543780613) which makes accessing `SOURCE_DATE_EPOCH` troublesome.

```

```meson

date_exe = find_program('date')

cmd = run_command('sh', '-c', 'echo $SOURCE_DATE_EPOCH')

source_date_epoch = cmd.stdout().strip()

### C

```

```c

#include <errno.h>

#include <limits.h>

#include <stdlib.h>

If you want less verbose code and are happy with the assumptions stated below, you can use

```

```c

#include <stdlib.h>

time_t now;

### C++

```

```cpp

#include <sstream>

#include <iostream>

#include <cstdlib>

### Go

```

```go

import (

        "fmt"

        "os"

### PHP

```

```php

\date('Y', (int)\getenv('SOURCE_DATE_EPOCH') ?: \time())

```

### Emacs-Lisp

```

```elisp

(current-time-string

  (when (getenv "SOURCE_DATE_EPOCH")

    (seconds-to-time

### OCaml

```

```ocaml

let build_date =

  try

    float_of_string (Sys.getenv "SOURCE_DATE_EPOCH")

### Java / gradle

```

```groovy

def buildDate = System.getenv("SOURCE_DATE_EPOCH") == null ?

  new java.util.Date() :

  new java.util.Date(1000 * Long.parseLong(System.getenv("SOURCE_DATE_EPOCH")))

### Javascript / node.js

```

```javascript

var timestamp = new Date(process.env.SOURCE_DATE_EPOCH ? (process.env.SOURCE_DATE_EPOCH * 1000) : new Date().getTime());

// Alternatively, to ensure a fixed timezone:

### Coffeescript

```

```coffeescript

now = new Date()

if process.env.SOURCE_DATE_EPOCH

  now = new Date((process.env.SOURCE_DATE_EPOCH * 1000) + (now.getTimezoneOffset() * 60000))

### Ruby

```

```ruby

if ENV['SOURCE_DATE_EPOCH'].nil?

  now = Time.now

else

};

```

or

```rust

use chrono::{DateTime, NaiveDateTime, Utc};

use std::env;

Add the following property in the `pom.xml` file:

```

```xml

<properties>

    <project.build.outputTimestamp>

        ${env.SOURCE_DATE_EPOCH}

Set the following properties for the Zip Task that creates the `.jar` file:

```

```groovy

// Normalizes the ZIP and JAR archives

tasks.withType(Zip) {

   preserveFileTimestamps = false

`debian/strip-nondeterminism/a2x`:

```

```sh

#!/bin/sh

# Depends: faketime

# Eventually the upstream tool should support SOURCE_DATE_EPOCH internally.

`debian/rules`:

```

```make

export PATH := $(CURDIR)/debian/strip-nondeterminism:$(PATH)

```

4. If none of the above options are good (you should have a ''very good reason'') then package maintainers may set and export this variable manually in `debian/rules`:

 ```

```make

export SOURCE_DATE_EPOCH ?= $(shell dpkg-parsechangelog -STimestamp)

```

If you need/want to support dpkg versions earlier than 1.18.8:

 ```

```make

export SOURCE_DATE_EPOCH ?= $(shell dpkg-parsechangelog -SDate | date -f- +%s)

```

If you need/want to support dpkg versions earlier than 1.17.0:

 ```

```make

export SOURCE_DATE_EPOCH ?= $(shell dpkg-parsechangelog | grep -Po '^Date: \K.*' | date -f- +%s)

```

To set `SOURCE_DATE_EPOCH` to the last modification of a Git repository you can use `git log`. For example:

```

```make

export SOURCE_DATE_EPOCH=$(git log -1 --pretty=%ct)

```