The position behind the sign
Every list gives this date as Pisces and stops. The measurable detail is the longitude: at noon, in every year from 1930 to 2035, the Sun on 1 March has stood between about ten degrees and eleven point four degrees of Pisces.
Ten degrees is where the second decan begins, so this date clears the first band in essentially every year. It is a more informative statement than the sign alone, because the sign covers a month of birthdays while the degree changes daily.
It also explains why two people who share this birthday can hold measurably different positions. A year early in the leap cycle sits near the lower end of that band and a year late in it sits near the top, a gap of more than a degree.
Why Jupiter appears from two directions
Before the outer planets were discovered, Pisces was ruled by Jupiter, and traditional practice still uses that assignment alongside the modern one of Neptune. Separately, the Chaldean sequence runs through the thirty six decans in a fixed planetary order, and counting from the start of Aries brings Jupiter to the middle third of Pisces.
The two systems arrive there independently, which is why the tradition treats this band as Pisces in a comparatively undiluted form. The reading attached to it is generosity, breadth and a tolerance for the loosely defined, in contrast to the Saturn band before it. That is interpretation and is marked as such.
How steady the figure is
The spread of a degree and a half over more than a century is not luck. The Gregorian calendar was designed so that the average year matches the tropical year very closely, and the leap day is the mechanism that keeps them together.
In practice the solar position on a fixed date moves forward roughly a quarter of a degree in each common year and drops back by close to a degree at each leap day. The result is a small cycle around the same value. Your own place in that cycle depends on your birth year, which is one reason a calculated position is worth more than a printed range.
The century year rule, which drops the leap day in most years divisible by a hundred, trims the last of the error. That is the level of care built into the calendar, and it is what allows a birthday page to quote a stable figure at all.
The rest of the chart is still open
A date fixes the Sun and very little else. The Moon can be in different signs at different hours of the same 1 March, since it changes sign every two or three days. The rising sign depends entirely on the time and the latitude of birth, and the house framework follows from it.
The sun sign is therefore the placement shared with everyone born in the same few weeks, and the least individual thing in a chart rather than the most. The widget above works out your exact degree from your own year and birthplace and reports the distance to the nearest sign boundary, which on this date is wide.
If the hour is missing, the convention is to calculate for noon and treat hour dependent placements as provisional. On this date the Sun is unaffected by that choice and the Ascendant is entirely undetermined by it.
Questions people ask about this
Is 1 March Pisces or Aries?
Pisces. The Sun does not reach Aries until around 20 March, so this date is nowhere near that boundary in any year.
What degree is the Sun on 1 March?
Between about ten and eleven point four degrees of Pisces at noon across 1930 to 2035. Your own figure depends on the year, hour and place of birth.
What decan is a 1 March birthday?
The second decan of Pisces, from ten to twenty degrees. In the Chaldean order it is ruled by Jupiter, which is also the traditional ruler of the sign as a whole.
Does the doubled Jupiter mean anything?
Traditionally it is read as the band where the sign's own character is least modified. It is an interpretation drawn from the structure of the scheme rather than a measurement.
Who rules Pisces, Jupiter or Neptune?
Both, in different schemes. Jupiter is the traditional ruler and Neptune the modern one, and most contemporary practice quotes them together rather than choosing.
Can this date ever be in the first decan?
Only marginally, at the earliest hours of the years lowest in the leap cycle. The calculated degree settles it, and in the great majority of cases the answer is the second decan.