As la gleki discussed the year of the date, I suggest here the following lujvo.
na'arctodetri : the century of the date
na'ardetri : the year of the date
ma'irdetri : the month of the date
na'ardeidetri : the x1-th day of the year
ma'irdeidetri : the x1-th day of the month
jefydeidetri : the x1-th day of the week
na'arjefydetri : the x1-th week of the year
ma'irjefydetri : the x1-th week of the month
(The same system is applicable to the set of {tcika},{cacra},{mentu},{snidu}, though I will not duscuss them here.)
sa'u they will be defined as follows:
na'arctodetri
$x_1$ detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo na'acto be li pa bei $x_4$
$x_1$ (number) is the century of the date of event/state x_2, at location x_3, by calendar x_4.
na'ardetri
$x_1$ detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo nanca be li pa bei $x_4$
$x_1$ (number) is the year of the date of event/state x_2, at location x_3, by calendar x_4.
ma'irdetri
$x_1$ goi ko'a detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo mo'e ko'a moi be lu'i ro masti be li pa bei $x_4$ be'o poi pagbu lo nanca be li pa bei $x_4$
$x_1$ (number) is the month of the date of event/state x_2, at location x_3, by calendar x_4.
na'ardeidetri
$x_1$ goi ko'a detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo mo'e ko'a moi be lu'i ro djedi be li pa bei $x_4$ be'o poi pagbu lo nanca be li pa bei $x_4$
$x_1$ (number) is the date of the year of event/state x_2, at location x_3, by calendar x_4.
ma'irdeidetri
$x_1$ goi ko'a detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo mo'e ko'a moi be lu'i ro djedi be li pa bei $x_4$ be'o poi pagbu lo masti be li pa bei $x_4$
$x_1$ (number) is the date of the month of event/state x_2, at location x_3, by calendar x_4.
jefydeidetri
$x_1$ goi ko'a detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo mo'e ko'a moi be lu'i ro djedi be li pa bei $x_4$ be'o poi pagbu lo jeftu be li pa bei $x_4$
$x_1$ (number) is the date of the week of event/state x_2, at location x_3, by calendar x_4.
na'arjefydetri
$x_1$ goi ko'a detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo mo'e ko'a moi be lu'i ro jeftu be li pa bei $x_4$ be'o poi pagbu lo nanca be li pa bei $x_4$
$x_1$ (number) is the week of the year of event/state x_2, at location x_3, by calendar x_4.
ma'irjefydetri : the x1-th week of the month
$x_1$ goi ko'a detri $x_2$ boi $x_3$ boi $x_4$ .ije $x_1$ sinxa lo mo'e ko'a moi be lu'i ro jeftu be li pa bei $x_4$ be'o poi pagbu lo masti be li pa bei $x_4$
$x_1$ (number) is the week of the month of event/state x_2, at location x_3, by calendar x_4.
Then x1 of {masnPA} zi'evla will be expanded to strings with {ma'irdetri}, for example:
lo masnpa = lo se ma'irdetri be li pa .
If we create
{jednpa} for "the first day of a week",
{jefnpa} for "the first week of a month",
{detnpa} for "the first day of a month" etc.,
then the similar relations will be derived:
lo jednpa = lo se jefydeidetri be li pa
lo jefnpa = lo se ma'irjefydetri be li pa
lo detnpa = lo se ma'irdeidetri be li pa
and so on.
Similarly, if we create {de'i'a} {de'i'e} {de'i'i} {de'i'o} {de'i'u} of BAI, they will be defined as follows:
de'i'a li PA = fi'o na'arctodetri li PA (in the PA-th century)
de'i'e li PA = fi'o na'ardetri li PA (in the year PA)
de'i'i li PA = fi'o ma'irdetri li PA (in the PA-th month)
de'i'o li PA = fi'o ma'irdeidetri li PA (in the PA-th day of the month)
de'i'u li PA = fi'o jefydeidetri li PA (in the PA-th day of the week)
(I replaced here the meaning of {de'i'o} and {de'i'u} with each other.)
mu'o