<s>
A	O
digital	B-Application
calendar	I-Application
is	O
a	O
collaborative	B-Application
or	O
personal	O
time	B-Application
management	I-Application
software	O
with	O
a	O
calendar	B-Protocol
that	O
can	O
be	O
used	O
to	O
keep	O
track	O
of	O
planned	O
events	O
.	O
</s>
<s>
The	O
calendar	B-Protocol
can	O
also	O
contain	O
an	O
appointment	B-Application
book	I-Application
,	O
address	B-Operating_System
book	I-Operating_System
or	O
contact	B-Protocol
list	I-Protocol
.	O
</s>
<s>
Common	O
features	O
of	O
digital	B-Application
calendars	I-Application
are	O
that	O
users	O
can	O
:	O
</s>
<s>
There	O
are	O
several	O
varieties	O
of	O
digital	B-Application
calendars	I-Application
.	O
</s>
<s>
Some	O
have	O
the	O
ability	O
to	O
be	O
connected	O
or	O
synchronized	O
with	O
other	O
calendars	B-Protocol
across	O
different	O
vendors	O
.	O
</s>
<s>
The	O
iCalendar	O
1.0	O
and	O
2.0	O
specifications	O
and	O
its	O
associated	O
standards	O
have	O
been	O
a	O
cornerstone	O
of	O
the	O
standardization	O
and	O
interoperability	O
of	O
calendar	B-Application
software	I-Application
across	O
different	O
vendors	O
.	O
</s>
<s>
A	O
digital	B-Application
calendar	I-Application
can	O
be	O
viewed	O
as	O
an	O
extension	O
of	O
many	O
of	O
the	O
features	O
provided	O
by	O
time	B-Application
management	I-Application
software	O
such	O
as	O
desk	B-Application
accessory	I-Application
packages	O
and	O
computer	O
office	B-Application
automation	I-Application
systems	O
.	O
</s>
<s>
Today	O
,	O
digital	B-Application
calendars	I-Application
are	O
common	O
on	O
many	O
office	O
suites	O
for	O
personal	O
computers	O
(	O
desktop	O
and	O
laptop	O
)	O
as	O
well	O
as	O
smartphones	B-Application
and	O
tablets	O
.	O
</s>
<s>
In	O
the	O
1990s	O
and	O
early	O
2000s	O
,	O
digital	B-Application
calendars	I-Application
was	O
a	O
standard	O
feature	O
of	O
many	O
personal	B-Application
digital	I-Application
assistants	I-Application
(	O
PDAs	B-Application
)	O
and	O
enterprise	B-Application
digital	I-Application
assistants	I-Application
(	O
EDAs	O
)	O
.	O
</s>
<s>
Since	O
the	O
early	O
2000s	O
,	O
PDAs	B-Application
and	O
EDAs	O
have	O
been	O
replaced	O
by	O
smartphones	B-Application
and	O
tablets	O
with	O
similar	O
functionality	O
.	O
</s>
<s>
Calendar	B-Application
software	I-Application
can	O
include	O
several	O
features	O
.	O
</s>
<s>
An	O
appointment	O
calendar	B-Protocol
is	O
a	O
list	O
of	O
appointments	O
and	O
the	O
attendees	O
for	O
the	O
appointments	O
.	O
</s>
<s>
Some	O
appointment	O
software	O
has	O
the	O
ability	O
to	O
automatically	O
suggest	O
shortened	O
events	O
by	O
default	O
or	O
in	O
cases	O
when	O
there	O
are	O
back-to-back	O
meetings	O
in	O
a	O
calendar	B-Protocol
.	O
</s>
<s>
For	O
example	O
,	O
instead	O
of	O
a	O
30	O
minute	O
meeting	O
at	O
13:00	O
,	O
a	O
calendar	B-Application
software	I-Application
may	O
suggest	O
that	O
an	O
event	O
is	O
shortened	O
to	O
25	O
minutes	O
and	O
either	O
starts	O
late	O
(	O
for	O
example	O
5	O
minutes	O
late	O
at	O
13:05	O
)	O
or	O
ends	O
early	O
(	O
for	O
example	O
13:25	O
)	O
.	O
</s>
<s>
Different	O
period	O
views	O
is	O
a	O
feature	O
which	O
allow	O
users	O
to	O
select	O
how	O
their	O
calendar	B-Protocol
is	O
displayed	O
:	O
one	O
day	O
,	O
a	O
work	O
week	O
,	O
one	O
week	O
,	O
one	O
month	O
,	O
one	O
year	O
,	O
etc	O
.	O
</s>
<s>
Many	O
digital	B-Application
calendars	I-Application
have	O
the	O
option	O
of	O
exporting	O
the	O
calendar	B-Protocol
to	O
various	O
file	O
formats	O
,	O
including	O
the	O
iCalendar	O
standard	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
the	O
user	O
can	O
,	O
for	O
example	O
,	O
take	O
the	O
calendar	B-Protocol
with	O
them	O
from	O
one	O
computer	O
to	O
another	O
,	O
or	O
from	O
an	O
old	O
e-mail	O
account	O
to	O
a	O
new	O
one	O
.	O
</s>
<s>
It	O
also	O
makes	O
it	O
possible	O
to	O
share	O
a	O
calendar	B-Protocol
with	O
others	O
at	O
a	O
given	O
point	O
in	O
time	O
.	O
</s>
<s>
Some	O
calendar	B-Protocol
tools	O
allow	O
the	O
user	O
to	O
publish	O
select	O
calendar	B-Protocol
information	O
on	O
a	O
public	O
link	O
.	O
</s>
<s>
With	O
digital	B-Application
calendars	I-Application
,	O
it	O
is	O
possible	O
to	O
do	O
this	O
interactively	O
and	O
with	O
the	O
option	O
of	O
sharing	O
your	O
availability	O
and	O
reserved	O
time	O
with	O
others	O
.	O
</s>
<s>
Availability	O
and	O
capacity	O
checking	O
is	O
an	O
advanced	O
function	O
which	O
can	O
check	O
the	O
availability	O
of	O
all	O
other	O
employee	O
and	O
resource	O
calendars	B-Protocol
in	O
a	O
group	O
,	O
and	O
which	O
may	O
be	O
useful	O
assigning	O
work	O
decide	O
on	O
projects	O
as	O
part	O
of	O
resource	O
planning	O
.	O
</s>
<s>
Collaborative	B-Application
scheduling	I-Application
means	O
that	O
the	O
software	O
suggests	O
meeting	O
times	O
when	O
all	O
participants	O
are	O
free	O
.	O
</s>
<s>
In	O
order	O
for	O
the	O
software	O
to	O
be	O
able	O
to	O
propose	O
meeting	O
times	O
for	O
participants	O
across	O
different	O
organisations	O
,	O
the	O
invitees	O
 '	O
calendars	B-Protocol
must	O
be	O
set	O
up	O
to	O
share	O
outside	O
their	O
organisation	O
when	O
they	O
are	O
free	O
.	O
</s>
<s>
A	O
group	O
calendar	B-Protocol
is	O
a	O
calendar	B-Protocol
which	O
displays	O
events	O
for	O
groups	O
in	O
addition	O
to	O
individual	O
calendars	B-Protocol
.	O
</s>
<s>
A	O
user	O
can	O
have	O
multiple	O
calendars	B-Protocol
that	O
can	O
be	O
toggled	O
on	O
and	O
off	O
.	O
</s>
<s>
This	O
function	O
makes	O
it	O
possible	O
to	O
categorize	O
different	O
events	O
into	O
separate	O
calendars	B-Protocol
(	O
such	O
as	O
work	O
calendar	B-Protocol
,	O
sports	O
calendar	B-Protocol
,	O
children	O
school	O
calendar	B-Protocol
)	O
.	O
</s>
<s>
Calendars	B-Protocol
themselves	O
can	O
basically	O
be	O
seen	O
as	O
a	O
passive	O
reminder	O
that	O
the	O
user	O
has	O
to	O
check	O
themselves	O
,	O
and	O
can	O
be	O
seen	O
as	O
a	O
form	O
of	O
reminder	B-Application
software	I-Application
.	O
</s>
<s>
It	O
is	O
often	O
also	O
possible	O
to	O
set	O
up	O
active	O
reminders	B-Application
.	O
</s>
<s>
Events	O
for	O
which	O
reminders	B-Application
are	O
wanted	O
may	O
include	O
birthdays	O
,	O
holidays	O
,	O
anniversaries	O
,	O
or	O
various	O
one-off	O
events	O
.	O
</s>
<s>
Calendars	B-Protocol
are	O
often	O
supplied	O
with	O
a	O
number	O
of	O
pre-installed	O
events	O
(	O
such	O
as	O
national	O
holidays	O
)	O
and	O
allow	O
the	O
user	O
to	O
create	O
their	O
own	O
events	O
.	O
</s>
<s>
Context-aware	O
reminder	O
systems	O
can	O
set	O
reminders	B-Application
based	O
on	O
the	O
user	O
's	O
current	O
location	O
.	O
</s>
<s>
Calendars	B-Protocol
can	O
be	O
set	O
up	O
with	O
international	O
or	O
regional	O
settings	O
.	O
</s>
<s>
Which	O
settings	O
become	O
active	O
may	O
depend	O
on	O
settings	O
in	O
the	O
computer/smartphone	O
,	O
settings	O
in	O
the	O
browser	B-Application
,	O
settings	O
in	O
the	O
user	O
profile	O
on	O
the	O
calendar	B-Application
application	I-Application
,	O
settings	O
in	O
the	O
profile	O
of	O
the	O
user	O
principal	O
name	O
,	O
or	O
(	O
typically	O
on	O
a	O
work	O
accounts	O
)	O
that	O
certain	O
settings	O
are	O
controlled	O
by	O
the	O
organisation	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
start	O
the	O
counting	O
on	O
the	O
first	O
full	O
week	O
of	O
the	O
year	O
(	O
DOT	O
calendar	B-Protocol
and	O
the	O
U.S.	O
broadcast	O
calendar	B-Protocol
)	O
,	O
or	O
traditional	O
western	O
counting	O
(	O
before	O
ISO	O
)	O
,	O
or	O
a	O
separate	O
variant	O
for	O
the	O
Middle	O
East	O
.	O
</s>
<s>
With	O
metric	O
units	O
the	O
corresponding	O
units	O
will	O
be	O
Celsius	B-Operating_System
,	O
meters	O
per	O
second	O
(	O
or	O
kilometers	O
per	O
hour	O
)	O
,	O
and	O
meters/kilometers	O
.	O
</s>
<s>
In	O
the	O
U.S.	O
,	O
respectively	O
,	O
the	O
units	O
would	O
be	O
Fahrenheit	B-Library
,	O
miles	O
per	O
hour	O
,	O
and	O
statute	O
miles/yards/feet	O
.	O
</s>
<s>
It	O
is	O
a	O
common	O
functionality	O
to	O
have	O
a	O
calendar	B-Protocol
on	O
computers	O
and	O
smartphones	B-Application
,	O
often	O
via	O
locally	O
installed	O
email	O
programs	O
or	O
webmail	O
that	O
can	O
be	O
accessed	O
with	O
a	O
standard	O
browser	B-Application
.	O
</s>
<s>
Some	O
examples	O
of	O
locally	O
installed	O
applications	O
for	O
individual	O
use	O
are	O
the	O
Lightning	B-Language
extension	O
for	O
Mozilla	B-Application
Thunderbird	I-Application
,	O
Microsoft	B-Application
Outlook	I-Application
without	O
Exchange	O
Server	O
,	O
or	O
Windows	B-Protocol
Calendar	I-Protocol
.	O
</s>
<s>
Examples	O
of	O
calendars	B-Protocol
which	O
allow	O
the	O
sharing	O
of	O
information	O
between	O
users	O
are	O
,	O
for	O
example	O
,	O
Mozilla	B-Language
Sunbird	I-Language
,	O
Windows	O
Live	O
Calendar	B-Protocol
,	O
Google	B-Application
Calendar	I-Application
,	O
or	O
Microsoft	B-Application
Outlook	I-Application
with	O
Exchange	O
Server	O
.	O
</s>
<s>
Web-based	B-Application
interfaces	O
allow	O
users	O
to	O
access	O
their	O
calendars	B-Protocol
from	O
any	O
computer	O
,	O
tablet	O
or	O
mobile	O
phone	O
with	O
a	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
This	O
can	O
be	O
implemented	O
for	O
most	O
calendars	B-Protocol
which	O
can	O
be	O
accessed	O
over	O
the	O
internet	O
.	O
</s>
<s>
An	O
online	B-Application
calendar	I-Application
is	O
a	O
web	B-Application
application	I-Application
that	O
allow	O
one	O
or	O
more	O
users	O
to	O
edit	O
,	O
and	O
optionally	O
share	O
with	O
other	O
users	O
,	O
online	O
access	O
to	O
a	O
digital	B-Application
calendar	I-Application
.	O
</s>
<s>
Online	B-Application
calendars	I-Application
that	O
are	O
free	O
to	O
use	O
include	O
Google	B-Application
Calendar	I-Application
,	O
Yahoo	B-Application
Calendar	I-Application
,	O
Windows	B-Protocol
Calendar	I-Protocol
and	O
Dayhaps	O
Calendar	B-Protocol
.	O
</s>
<s>
Online	B-Application
calendars	I-Application
that	O
provide	O
an	O
email	O
reminder	O
service	O
:	O
Google	B-Application
Calendar	I-Application
,	O
Outlook	O
Calendar	B-Protocol
,	O
DayViewer	O
and	O
Calendar.online	O
.	O
</s>
