Time
is one of the few Imperial or Standard measures still used in the Metric
System.
There are proposals for metric time where a day is divided into 10 hours;
an hour into 100 minutes; etc. but that is not in general use.
The shorter intervals like nanoseconds and femtoseconds are used in computers
and laser technology while light years and astronomical units are used
in space research.
There are 1,000 milliseconds in 1 second; 1,000 microseconds in 1 millisecond;
and so on.
NOTE:- A millisecond is one thousandth of a second, NOT one millionth.

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.

We have tried
to be accurate with the above table but cannot be held responsible for
inaccuracies.
Go back to first principals and double check your calculations if the
result is 'mission critical'.

Remember that
you cannot create energy only convert it. Likewise, you will not find
a conversion from pounds to metres - the basic units must remain the same
- mass converted to mass, length converted to length, et al.

You won't usually find a conversion from kilograms to grams - the prefix
'kilo' means '1,000' so a kilogram is in fact 1,000 grams in the same
way as a kilometer is 1,000 metres [or about 1,000 yards in 'old money'].
I have put a few in the tables because visitors have asked for them. More
prefixes can be found on another table.

One handy metric link between units to remember is that 1 Litre [1000cc]
of pure water weighs 1 kilogram.

If accuracy is critical beware of old versions of MS Excel which had problems
rounding off numbers.