I do not know the picking pattern for it but you can strum if u want to thats how i do it! 

 The chords are:

G B7 C D
Today it was your birthday
And I didn?t know what to do
Are you supposed to call the people you love
When you know they don?t love you

G B7 C D
Today was your birthday
But I didn?t dare to call
Though I thought about you all day
Even at midnight I wanted to call
To be honored to be the first one to send you my love
And wish you

G B7 C D
Happy hippy birthday
Happy hippy birthday
Happy hippy birthday
Happy hippy birthday

G B7 C D
35 candles on a cake
That I will never taste
35 candles run away
That I picture in my head
35 years old and I?m 22
And I remember when you used to say
That I was young but you didn?t care at all

Happy hippy birthday
Happy hippy birthday
Happy hippy birthday
Happy hippy birthday

G B7 C D
16 of June 1973
My parents hadn?t even met
16 of June 1973
Was born the only boy I can ever love

C D G C
We?re 13 years apart
Like my parents were
C D G
They?re 13 years apart and for them it?s worked out
C D G B7
They had me and my brother
They had me and my brother as achievements of their love
C D G
They had me and my brother
They had me and my brother
(just stay with G from prevoius verse)
G B7 C D until end
My father loved my mother so
That he would never let her down
My mother loved my father so
That she would never let him down

She loved him until the day he died
Until the day he died
Until the day he died
She will love him until the day she dies
Until the day she dies
Until the day she dies
You could love me till the day you die
Until the day you die
Until the day you die
Cause I will love you till the day I die
Until the day I die
Until the day I die
And even more.