Remind allows you to remind yourself of upcoming events and appointments. Each reminder or alarm can consist of a message sent to standard output, or a program to be executed. It also features: sophisticated date calculation, moon phases, sunrise/sunset, Hebrew calendar, alarms, PostScript output and proper handling of holidays.

Gcal is a program to calculate and print calendars on the command-line. Calendars can be printed in 1-month, 3-month or whole-year views. In addition, eternal holiday lists can be generated for many countries, which can be complemented by user-made lists of fixed dates to make an agenda. Gcal can also calculate astronomical data, such as the phases of the moon, and supports alternative calendar formats: Julian, Gregorian, Islamic, Chinese and more.

adl-submit is a tool that can be used to submit events to any instance of the Agenda Du Libre (a web calendar originally meant for free software events). Users can set fields through the command line or create an XML that can be submitted with the adl-submit tool. While the Agenda Du Libre web application is available in multiple languages, most of the events on https://www.agendadulibre.org are in French and the adl-submit tool is only available in French.

ConfClerk is an application written in Qt, which makes conference schedules available offline. It displays the conference schedule from various views, support searches on various items (speaker, speech topic, location, etc.) and enables you to select favorite events and create your own schedule.

At the moment ConfClerk is able to import schedules in XML format created by the PentaBarf conference management system (or frab) used by e.g. FOSDEM, DebConf, FrOSCon, Grazer LinuxTage, and the CCC congresses.

ConfClerk is targeted at mobile devices but works on any system running Qt.

Hebcal is a program for converting between Hebrew and Gregorian dates, and generating lists of Jewish holidays for a given year. Shabbat, holiday candle lighting, and havdalah times are approximated using your location.

It can also show daily prayer times, the weekly Torah reading, and the daily leaf of Talmud. The program can help with counting of the Omer or with calculation of Hebrew yahrzeits, birthdays, or anniversaries.

By default, date2name gets the modification time of matching files and directories and adds a datestamp in standard ISO 8601+ format YYYY-MM-DD at the beginning of the file or directory name.

Date is a header only C++ library that extends the chrono date algorithms library for calendar dates and durations. It also provides the <tz.h> library for handling time zones and leap seconds.

gsimplecal is a lightweight calendar application written in C++ using GTK. Launched once, it pops up a small calendar applet, launched again it closes the running instance. It can additionally be configured to show the current time in different timezones.

Khal is a standards based console calendar program, able to synchronize with CalDAV servers through vdirsyncer. It includes both a CLI and a TUI named 'ikhal'.

LibHdate is a small library for the Hebrew calendar and times of day, written in C, and including bindings for C++, pascal, perl, php, python, and ruby. It includes two illustrative command-line programs, hcal and hdate, and some snippets and scripts written in the binding languages.

ccal is a command line program which writes a Gregorian calendar together with Chinese calendar to standard output. Its usage is similar to the cal program. In addition to console output, it can also generate Encapsulated Postscript and HTML table outputs for use in do-it-yourself calendars and web pages. It supports both simplified and traditional Chinese characters.

Ccache is a compiler cache. It speeds up recompilation by caching previous compilations and detecting when the same compilation is being done again. Supported languages are C, C++, Objective-C and Objective-C++.

cdrecord converts a CD image in a ".bin / .cue" format (sometimes ".raw / .cue") to a set of .iso and .cdr tracks.

cd-discid is a command-line tool to retrieve CDDB discid information from an audio CD.

Optical media (CD,DVD,BD) keep their data only for a finite time (typically for many years). After that time, data loss develops slowly with read errors growing from the outer media region towards the inside.

Dvdisaster stores data on CD/DVD/BD (supported media) in a way that it is fully recoverable even after some read errors have developed. This enables you to rescue the complete data to a new medium.

Data loss is prevented by using error correcting codes. Error correction data is either added to the medium or kept in separate error correction files. Dvdisaster works at the image level so that the recovery does not depend on the file system of the medium. The maximum error correction capacity is user-selectable.

DVDStyler is a DVD authoring application which allows users to burn video files in many formats to DVD discs, complete with individually designed menus. It can be used to create professional-looking DVD's with custom buttons, backgrounds and animations, from within a user-friendly graphical interface.

cdrtools is a collection of command line utilities to create CD's, DVD's or Blue Ray discs. The most important components are cdrecord, a burning program, cdda2wav, a CD audio ripper which uses libparanoia, and mkisofs, which can create various disc images.

Asunder is a graphical audio CD ripper and encoder. It can save audio tracks as WAV, MP3, Ogg Vorbis, FLAC, Opus, Wavpack, and Musepack. It can use CDDB to name and tag each track automatically, and it allows for each track to be by a different artist. Asunder can encode to multiple formats in one session, and it can create M3U playlists.

CDemu is a software suite designed to emulate an optical drive and disc (including CD-ROMs and DVD-ROMs).

The GNU Compact Disc Input and Control Library (libcdio) is a library for CD-ROM and CD image file access. It allows the developer to add CD access to an application without having to worry about the OS- and device-dependent properties of CD-ROM or the specific details of CD image formats. It includes pycdio, a Python interface to libcdio, and libcdio-paranoia, a library providing jitter-free and error-free audio extraction from CDs.

RipIT is used to extract audio from CDs.

cdrdao records audio or data CDs in disk-at-once (DAO) mode, based on a textual description of the contents. This mode writes the complete disc – lead-in, one or more tracks, and lead-out – in a single step and is commonly used with audio CDs. cdrdao can also handle the bin/cue format, commonly used for VCDs or disks with subchannel data.

Libcddb is a C library to access data on a CDDB server (freedb.org). It allows you to:

1. search the database for possible CD matches;

2. retrieve detailed information about a specific CD;

3. submit new CD entries to the database.

Libcddb supports both the custom CDDB protocol and tunnelling the query and read operations over plain HTTP. It is also possible to use an HTTP proxy server. If you want to speed things up, you can make use of the built-in caching facility provided by the library.

libudfread is a C library for reading UDF file systems. UDF is a file system mostly used for DVDs and other optical media. It supports read-only media (DVD/CD-R) and rewritable media that wears out (DVD/CD-RW).