fractions
of a second 
metric
name 
0,000
000 000 000 000 000 000 001 
yoctosecond
[ ys ] 
0,000
000 000 000 000 000 001 
zeptosecond [ zs ] 
0,000
000 000 000 000 001 
attosecond
[ as ] 
0,000
000 000 000 001 
femtosecond [ fs ] 
0,000
000 000 001 [ trillionth ] 
picosecond
[ ps ] 
0,000
000 001 [ billionth ] 
nanosecond [ ns ] 
0,000
001 [ millionth ] 
microsecond
[ µs
] 
0,001
[ thousandth ] 
millisecond [ ms ] 
0.01
[ hundredth ] 
centisecond
[ cs ] 
1.0 
second [ s ] 
seconds
to years 

60 seconds 
= 1 minute
[ mean solar ] 
59.83617 seconds 
= 1 minute [ sidereal
] 
60 minutes 
= 1 hour 
24 hours 
= 1 day 
3,600
seconds 
= 1 hour 
86,400 seconds 
= 1 day [ mean solar
] 
86,164.09
seconds 
= 1 day
[ sidereal ] 
7 days 
= 1 week 
168 hours 
= 1 week 
14 days 
= 1 fortnight 
28, 29,
30 or 31 days 
= 1 month 
365 days 
= 1 year 
366 days 
= 1 leap
year 
12 months 
= 1 year 
31,536,000
seconds 
= 1 year
[ calendar ] 
31,558,150 seconds 
= 1 year [ sidereal ] 
31,556,930
seconds 
= 1 year
[ tropical ] 
9,460,550,000,000,000
metres 
= 1 light year 
299,792,458
metres per second ( m/s ) 
= speed of light 
parsec 
= approx. 3.25 light
years 
year
intervals  anniversaries 
number
of years 
Biennial 
2

Triennial 
3

Quadrennial 
4

Quinquennial 
5

Hexennial
* 
6

Septennial 
7

Octennial 
8

Novennial 
9

Decennial 
10

Hendecennial
* 
11

Duodecennial 
12

Tredecennial
* 
13

Quindecennial 
15

Sextodecennial
* 
16

Septendecennial 
17

Vigintennial
* 
20

Trigentennial
* 
30

Quadragennial 
40

Quinquagenary 
50

Sexagennial
* 
60

Septuagennial
* 
70

Septuagesiquintennial
* 
75

Octogintennial
* 
80

Nonagintennial
* 
90

Centennial 
100

Quasquicentennial 
125

Sesquicentennial 
150

Terquasquicentennial
or Septaquintaquinquecentennial * 
175

Bicentennial 
200

Quasquibicentennial
* 
225

Semiquincentennial
* 
250

Tercentennial 
300

Semiseptcentennial
* 
350

Quatercentenary 
400

Quincentennial 
500

Sexcentennial
* 
600

Septcentennial
* 
700

Octocentennial 
800

Millenial 
1,000

Quindecimillenial 
15,000

Note:
Interval names marked with a * do not appear in major dictionaries
but follow a logical linguistic progression. Thanks to Glenn
Kersten for the bulk of the data on anniversaries. 




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pages 

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useful sites 


